Bioactivity of Marine Organisms

4.1 Seaweeds

The green, brown and red algae have been extensively screened for antibacterial and antifungal activity.1 The active principles isolated from Symphycladia gracillis, Rhodomela larix and Polysiphonia lanosa39'41 are 2,3-dibromobenzyl alcohol, 4,5-disulphate dipotassium salt, 2,3-dibromo-4,5-dihydroxybenzaldehyde, 2,3-dibromo-4,5-dihydroxybenzyl alcohol, 3,5-dibromo-p-hydroxybenzyl alcohol, and 5-bromo-3,4-dihydroxybenzaldehyde. Virtually nothing is known about the physiological importance of these bromophenols. However, their antialgal activity suggests that they may play a role in the regulation of epiphytes and endophytes.

4.2 Seaweeds of Indian Coasts

Several seaweeds have shown a wide range of bioactive properties.1,42-49 Hemolytic and antimicrobial activities are reported in seaweeds collected from Mandapam, Tamil Nadu, the Gulf of Manner and Back Bay, India.50 The extracts of seaweeds, in general, are found active against Gram-negative microbes. The extract of Enteromorpha compressa, Cladophoropsis zollinger, Padina gymnospora, Sargassum wightii and Gracilaria corticata are found active against the Gram-positive cultures of Bacillus. High order of hemolytic activity is shown by the extracts of Cladophoropsis zoolingeri and Grateloupia lithophila.

Extracts of 25 seaweeds from the Indian coast have been put through a broad biological screen which includes tests for antiviral, antibacterial, antifungal, antiprotozoal, antifertility activities, and a wide range of pharmacological activities. Significant activity is found in 13 seaweeds, the most promising activity being 100% antifertility (antiimplantation) activity observed in three species.51 The seaweeds which showed biological activities are: Caulerpa racemosa (Chlorophyceae) collected from Malvan in November exhibited hypotensive activity (90 mm, 5 mg/kg), LD50 93.75 (mg/kg in mice), Cladophorapinnulata (Chlorophyceae) from Baga, Goa, in December was found toxic, LD50 8.25 (mg/kg, in mice). Codium elongatum (Chlorophyceae) collected from Cabo de Rama, Goa, India, in February showed antiviral activity (50%, 1 mg), LD50 681 (mg/kg, in mice). Enteromorpha spp. (Chlorophyceae) collected from Cabo de Rama, Goa, India, Showed diuretic activity (112%, 170 mg/kg), LD50 681 (mg/kg in mice). The other green algae, Caulerpa surtularioides collected from Malvan, Maharashtra in November, Chaetomorpha media from Vengurla, Maharashtra in May; Enteromorpha intestinalis from Chaopora, Goa, in February and Ulva fasciata from Baga, Goa in December were found devoid of activity. The alga Trichodesmium erythraeum (Cyanophyta) collected from Mandovi, Goa, in March exhibited diuretic activity (104%, 170 mg/kg), LD50 681 (mg/ kg, in mice), whereas the alga Trichodesmium erythraeum (Cyanophyta) from Aguada, Goa, in April was found devoid of activity. The brown algae Stoechospermum marginatum collected from Dona Paula, Goa in December showed spasmolytic activity (50%, 50 ^g/ml), LD50 more than 1000 (mg/kg, in mice), Padina tetrastromatica collected from Baga, Goa, in January exhibited spasmogenic activity (50 ^g/ml) and antifertility activity (100%, 200 mg/kg), LD50 464 (mg/kg, in mice); Sargassum tenerrimum from Baga, Goa, in December showed CNS depressant activity (89 mg/kg), LD50 178 (mg/kg in mice). The brown algae Chnoospora implexa collected from Mandapam, Tamilnadu, in March, Dictyota bartayresiana from Anjuna, Goa, in January and Spatoglossum asperum from Baga, Goa, in December did not show any activity.

The red algae which exhibited activity are: Acantophora specifera from Baga, Goa, in February showed antifertility activity (100%, 200 mg/kg in mice), LD50 more than 1000 (mg/kg, in mice), Chondria armata from Baga, Goa, in December exhibited hypotensive activity (40 mm, 1 mg/kg, 200 min) LD50 1 78 (mg/kg, in mice); Corallina spp. from Anjuna, Goa, in January showed spasmogenic and oxytocic activities (50 ^g/ml), LD50 681 (mg/kg, in mice) and Hypnea musciformis from Baga, Goa, in December showed diuretic activity (130%, 250 mg/kg), LD50 more than 1000 (mg/kg, in mice), Gelidiella acerosa from Eravali, Tamilnadu, in December showed antifertility activity (100%, 100 mg/kg, in mice). The red algae Gelidiella spp. collected from Baga, Goa, in November, Gracilaria corticata from Baga, Goa, in November and Hypnea musciformis var. cervicornis from Malvan, Maharashtra in November did not show any activity. The sea grasses Diplanthera universe collected from Mandapam, Tamilnadu, in March and Thalassia hemprichii from Mandapam, Tamilnadu, in March did not show any activity.

Several members of the red, brown and green algae, which were screened, are reported to show a broad spectrum of biological activities. Some of the species that were examined were also tested earlier by other workers, but none of the activities were observed. For instance, extracts of Chondrus crispus and Gelidium cartilagineum have been found to be active against influenza B and mumps virus. This activity has been attributed to the presence of galactan unit in the polysaccharides, agar and carrageenan present in both the species. Based on this, one may expect Hypnea musciformis, Gelidiella spp. and Gracilaria corticata which are well-known sources of these polysaccharides to exhibit similar activity. Unfortunately, the extracts of these algae have not been tested against the above virus. However, they have been found inactive against Ranikhet disease virus, Vaccinia virus and Semiliki forest virus. The absence of the antiviral activity may be attributed to the varying solubility behaviour of the sulphated polysaccharide, responsible for the activity in aqueous ethanolic solutions or to the well known variation in phytoconstituents depending upon the ecological factors prevailing at the time of collection and upon the growth stage of the plant. The last reason could also be applicable to the differences in activity of two different samples of Enteromorpha spp. and Hypnea musciformis collected at different places. The extract of Sargassum tenessimum was not found to have any chemotherapeutic activity though the species of this genus have been reported to possess antibiotic effects due to the presence of antibiotic substances sarganin-A and sarganin-B. This activity, however, seems to be seasonal, and has been reported to decrease directly with plant vigour as a function of latitude.52

Acute poisoning from seaweeds has not been reported in the literature, but it has been mentioned that Caulerpa, one of the most popular edible algae in the Philippines is considered toxic during the rainy season. This toxicity has been attributed to the presence of caulerpicin which has been found to have neurotropic effects.3 Unfortunately, the test for this activity has not been performed for the extract from Caulerpa racemosa which was collected during the pre-monsoon season. Since caulerpin is not reported to possess hypotensive activity, the effect observed in this species seems to be due to some other constituent. This inference is further supported by the absence of similar activity in Caulerpa sertularioides considering that caulerpicin is a common constituent of both the species.

The most promising activity is, perhaps, the antiimplantation activity found in three species, viz. Padina tetrastromatica, Acantophora specifera and Gelidiella acerosa. Preliminary experiments conducted on mice have shown that these extracts are 100% active. The occurrence of such activity in seaweeds has not been reported hitherto in the literature.

Palytoxin, the toxin principle of the soft coral Palythoa toxica,53 has also been found in seaweed Chondria armata.26 Extensive pharmacological/ biochemical studies have been carried out on palytoxin, such as membrane depolarisation, Na+ or Ca2+ influx, stimulation of arachidonic acid release, stimulation of neurotransmitter release, inhibition of Na+/K+-ATPase induction of contraction of smooth muscle and tumor-promising, while it is believed that palytoxin acts through Na+/K+-ATPase. However, detailed mechanism of its action is still unknown.26

Microalgae are frequently involved in various forms of seafood poisoning. However, poisoning due to macroalgae are rare. Human intoxication due to ingestion of the red alga Polycavernosa tsudai (formerly Gracilaria edulis) occurred in Guam in 1991. Thirteen people became ill, three of whom died.26 A novel glycosidic macrolide, polycavernoside A54-58 has been isolated from the red alga, and is believed to be responsible for the poisoning. The content of polycavernoside A in the alga was low, but it caused in mice symptoms comparable with those observed in human patients. The sudden and transient occurrence of polycavernoside A in the alga remains unexplained. Previous outbreaks of fatal poisoning caused by G. chorda and G. verrucosa also remain unexplained as to the nature of the toxin(s). The red alga Chondria armata is a folk medicine used as an anthlmintic. Two palytoxin analogs, domoic acid and its seven derivatives are isolated from the alga.59-64 No incidence of poisoning due to this alga is known. However, domoic acid, produced by the diatoms Nitzschia pungens and Pseudonitzschia australis, has caused fatal food poisonings, after accumulating in shellfish. This recently described poisoning is termed amnesic shellfish poisoning. A related neurotoxic amino acid, kainic acid, also occurs in red alga but with no intoxication episode. Debromoaplysiatoxin has been isolated from the blue green alga Lyngya majuscula as a potent inflammatory agent, and is responsible for incidents of severe dermatitis among swimmers who have come in contact with the alga in Hawaii and Okinawa. Interestingly, debromoaplysiatoxin is reported to have tumour promoting activity which is identical to that shown by phorbol esters.26

Ethanolic extracts of the Indian marine algae have been tested for antiviral, antibacterial, antifungal, antifertility, hypoglycaemic and a wide range of pharmacological activities. Of 34 species screened 17 were found active. Six were diuretic, three hypoglycemic, three hypotensive, four exhibited antiimplantation activity. Cytokinin activity was observed in one, and one extract showed adrenergic blocking action. The extracts neither had antibacterial, antifungal and antiviral activities nor were found toxic.65 The green algae which exhibited activity are: Caulerpa taxifolia collected from Okha, Gujarat, in April showed hypotensive activity, LD50 825 (mg/kg, in mice). Halimeda macroloba from Andaman in February showed diuretic and antiimplantation activities: Monostroma spp. from Goa exhibited antiimplantation activity, LD50 681 (mg/kg, in mice); Pseudobryopsis spp. from Okha, Gujarat, showed hypoglycaemic activity, LD50 681 (mg/kg, in mice); Udotea indica from Porbander, Gujarat, showed cytokinin activity, LD50 1000 (mg/kg, in mice); Dictyopteris australis, the brown alga from Cabada, Gujarat exhibited diuretic and hypotensive activities, LD50 more than 1000 (kg/mg, in mice). The green algae Acetabularia crenulata from Andaman, Chamaedoria auriculata from Gujarat, Ulva reticulata from Andaman, Valoniopsis spp. from Tamilnadu and Valoniopsis pachynema from Gujarat did not show any activity.

The brown algae Iyengaria stellata from Gujarat showed adrenergic activity; Padina gymnospora from Gujarat exhibited hypoglycemic activity; LD50 1000 (mg/kg, in mice); Pocockiella variegata from Tamilnadu showed the CNS stimulant activity, LD50 1000 (mg/kg, in mice), Sargassum cinereum, Malvan, Maharasthra, also showed CNS stimulant activity and Spatoglossum asperum from Anjuna, Goa, exhibited antiimplantation and hypotensive activities, LD50 1000 (mg/kg, in mice). The brown algae Hydroclathrus clathratus from Dwarka, Gujarat, Sargassum wightii from Gulf of Manner, Tamilnadu, S. myriocystum from the same locality and Turbinaria decurrens from Andaman did not show any activity. The red algae Botryocladia leptopoda from Gujarat exhibited antiimplantation and CNS stimulant activities, LD50 825 (mg/kg, in mice); Gracilaria spp. collected from Andaman in February showed diuretic and hypotensive activities LD50 more than 1000 (mg/kg, in mice); Laurencia papillosa collected from Anjuna, Goa, exhibited diuretic activity, LD50 more than 1000 (mg/kg in mice); Scinaria hatei from Gujarat showed hypotensive activity, LD50 more than 1000 (mg/kg, in mice); Solieria spp. from Anjuna, Goa, showed diuretic and antiimplantation activities. LD50 3 1 6 (mg/kg, in mice), and Spyridia fusiformis from Andaman showed diuretic and hypoglycemic activities LD50 681 (mg/kg, in mice). The red alga Chondrococus spp. from Goa Galaxaura oblongata and G. rogosa from Andaman, Gastroclonium iyengarii, Gracilaria edulis and Halymenia venusta from Gujarat, Jania adhaerens from Mandapam, Tamilnadu and Spyridia insignis from Trivandrum, Kerala, did not show any activity.65 Seaweeds extracts are known to exhibit inhibitory effects upon a number of Gram-positive and Gram-negative bacteria, but none of the extracts screened showed antibacterial activity. The most promising activity observed was the antiimplantation activity found in four species, viz. Helimeda macroloba, Monostroma spp., Spatoglossum asperum and Botryoctadia leptopoda.

Alcoholic extracts of 50 Indian marine algae collected from the coasts of Goa, Maharashtra, Tamilnadu, Gujarat, Lakshadweep, Orissa and the Andaman and Nicobar Islands during pre-monsoon and post-monsoon periods have been tested for a wide range of biological activities. Of these, two extracts exhibited antiamoebic and antiviral activity each three of them had antiimplantation activity, nine had hypoglycaemic activity while hypotensive activity was associated with 11 extracts, 14 extracts were found to be diuretic and one of them had antiinflammatory activity. Further, ten of these extracts exhibited two types of activities, while a combination of 3 and 4 types of activities was observed in one extract each.66

Caulerpa taxifolia collected from Porbunder, Gujarat, exhibited hypotensive and diuretic activities. Several species of Caulerpa have been investigated and bioactive principles, such as caulerpin and caulerpinin have been isolated from a number of them. Caulerpin produces mild anaesthetic action, difficulty in breathing, sedation and loss of balance. The toxic syndrome has been reported to be somewhat similar to that produced by ciguatera fish poisoning. The neurotropic activity of caulerpicin is thought to be of clinical value. Tropical green algae, and a few of their temperate relatives have yielded a number of bioactive metabolites and some of these are believed to be used by the algae as a chemical defence against herbivorous animals. The characteristic feature of these metabolites is the presence of a 1,4-diacetoxybutadiene moiety which has been found in more than half of the compounds reported so far. Dictyota atomaria collected from Okha, Gujarat, exhibited hypotensive activity. Several diterpenes have been isolated from Dictyota species. Of these, some are found to have cytotoxic activity. The sex attractant isolated from Dictyota dichotoma is n-butylcyclohepta-2,5-diene. Several highly unsaturated hydrocarbons have been isolated from marine algae, and the function of these hydrocarbons have been studied.67 It has been found that the sperm cells aggregate around the female gametes of brown algae which exude C11 hydrocarbons that attract the former and cause them to remain in the excited state in the vicinity of the latter. Hydroxydictyodial isolated from Dictyota spinulosa inhibits feeding in omnivorous fish. Enteromorpha intestinalis collected from Chilka Lake, Orissa, exhibited antiamoebic, hypotensive and diuretic activities. No chemical investigation on this alga appears to have been carried out. It would be interesting to investigate this alga thoroughly. Alcoholic extracts of Halimeda gracilis collected from Lakshadweep, and H. opunita from the South Andaman Island, have shown diuretic and hypotensive activites. The alcoholic extract of Halimeda tuna from the South Andaman coast, exhibited only diuretic activity. The genus Halimeda has been found to contain highly active sesquiterpenes.26 Some of the diterpenes from Halimeda species are reported to exhibit cytotoxic and antimicrobial properties. Extract of Lyngbya confervoides from Lakshadweep has shown hypoglycaemic activity, which has not been reported from any species of Lyngbya. Several bioactive compounds have been isolated from Lyngbya majusculla6 which causes swimmers itch. Of the compounds isolated from this species lyngbyotoxin and bromoaplysiatoxin are highly toxic. Alcoholic extracts of Ulva faciata and Ulva lactua from the Gujarat coast exhibited antiviral and antiimplantation activities, respectively. The most interesting finding is that the alcoholic extract of the roots of Avicennia officinalis from the South Andaman Island, exhibited antiamoebic, hypoglycaemic, hypotensive and antiinflammatory activities which need to be investigated thoroughly. A. officinalis leaves extract exhibited moderate diuretic activity which was localised in the glycosidic fraction. Achrostichum aureum (family Pteridaceae), a mangrove from Jhirkatang, South Andaman, exhibited antifertility activity in female rats. The water soluble fraction of the ethanolic extract of the mangrove prevented (100%) pregnancy when administered to female rats on 1-7 post coitum. This fraction was found devoid of both estrogenic and antiestrogenic activities.69 These findings support the view that the antifertility activity of this plant may be due to certain properties other than estrogenicity/ antiestogenicity which need to be investigated.

There have been several reports of antiviral activity of seaweeds and seaweed extracts.70 It has been indicated that agar, which is used as a culture medium for microorganisms, is itself a source of some active components against myxovirus. Caccomese et al71 have studied the antiviral activity of marine algae from Eastern Sicily against tobacco mosaic virus, and Blunden et al72 have surveyed British marine algae for antiinfluenza virus activity.

Ethanolic extracts of the Indian marine algae belonging to the Rhodophyceae, Phaeophyceae, and Chlorophyceae have been tested against Semiliki forest (SFV), Ranikhet disease (RDV) and Vaccinia viruses (VV). Of the 31 seaweeds screened 17 showed activity of which seven were found active against SFV and ten against Vaccinia virus (VV). None of them showed antiviral activity against RDV. The antiviral activity observed in Codium elongatum and the two species of Hypnea was attributed to the polysaccharides.73 Of the active extracts, significant inhibition being exhibited by the green algae Ulva fasciata (70%, SFV) and Codium elongatum (50%, SFV and 45%, VV) and red algae Chondria armata (75%, SFV) Hypnea cervicornis (100% VV), Hypnea musciformis (50%, SFV and VV) and Spyridia insignis (50%, VV). Significant antiviral activity was also found in brown algae Sargassum myriocystum (75%, VV) and S. weightii (50%, VV). In the follow up studies, the activity was concentrated in water soluble fraction of the alcoholic extracts of Codium elongation and the two species of Hypnea. Subsequently it was found that the antiviral activity in the water soluble fraction was due to sulphated polysaccharides. Carrageenans from Chondrus crispus is known to be antiviral. The activity has been reported to be due to the sulphated galactose unit of the phycocolloid. Algal polysaccharides such as laminarin, fucoidan, and algin, which lack sulfated galactose unit exhibit no antiviral activity. It is interesting to note that in some cases, such as Hypnea, two different species belonging to the same genus showed antiviral activity. In other cases not all species belong to the same genus such as Sargassum and Galaxaura exhibited activity.

Indian seaweeds belonging to Rhodophyceae. Phaeophyceae and Chlorophyceae have also been screened for their effects on central nervous system. Of the 69 extracts screened, activity was observed in eight extracts. Among the active extracts six exhibited the CNS depressant activity.74 In the gross behaviour, most of the extracts exhibiting CNS activity with the exception of Sargassum tenerrimum and Caulerpa sertularioides showed a CNS stimulant action as evidenced by marked increase in spontaneous and locomotor activities, hyper sensitive to touch, pilo reaction, Straub' phenomenon and in certain cases (Ulva fasciata) preconvulsion clonic. Extracts of Sargassum tenerrimum and Caulerpa sertulariodes potentiated pentobarbital hypnosis and showed depression of both spontaneous and locomotor activities. S. tenerrimum also reduced to 41% the amphetamine induced hyperactivity. None of the five animals tested for forced locomotor activity (rotating test) could stay on the slowly rotating rod for two minutes when administered a dose of 89 mg/kg (ip) of S. tenerrimum extract. Thus, all the tests conducted indicated that C. sertulariodes and S. tenerrimum possess CNS depressant activity. The CNS simulant activity of Hypnea cervicornis was confirmed in a repeat collection when a dose of 76.6 mg/kg (ip) reversed, the fall in body temperature and completely counteracted aptosis and sedation. Similar effects were observed in benzene and water soluble fractions at a dose of 16, 5 and 232 mg/kg (ip), respectively. Its significant antireserpine activity added further interest this extract. Follow up studies of the water soluble fraction located the activity in the carrageenan component. In view of the CNS depressant activity exhibited by Caulerpa sertularioides, the extract was fractionated and the activity concentrated in the chloroform soluble fraction. Caulerpin, an ether soluble constituent of Caulerpa sertularioides,15 could be responsible for the observed depressant activity, as caulerpin has been reported to produce sedation.76-81 It is interesting to note that in contrast to depressant activity mostly observed in terrestrial plants, CNS stimulant activity predominates in seaweeds.

Marine algae from the French Mediterranean coast have been tested for antibacterial and antifungal activities.82 Seaweeds of South Florida have been evaluated for antimicrobial and antineoplastic activities.77 Carrageenan, a cell wall polysaccharide of marine red algae, exhibits several types of properties. It is co-internalised into infected cells with the Herpes simplex virus (HSV), and inhibits the growth of this DNA containing virus. Carrageenan interferes with fusion between cells infected with human immunodeficiency virus (HIV), an RNA-containing virus, and inhibits the retroviral enzyme (reverse transcriptase). The sulphated polysaccharides from red algae have a broad spectrum antiviral activity. There is considerable evidence to support that carrageenan bind to and modulate cell-cell interactions of various kinds, including sperm-egg fusion in the brown alga Fucus. It inhibits fertilisation in sea urchins, hamsters, and guinea pigs, embryogenesis in the green alga

Volvox, aggregation of isolated sponge cells. Degraded carrageenan is known to be a potent inflammatory agent in vivo. Hydrolysed carrageenans are used to induce intestinal inflammation in many animal models of inflammatory bowel diseases. Carrageenans are also reported to have long lasting effects on the immune system.79 It also induces inflammation and ulceration.80

4.3 Marine Invertebrates of Indian Coasts

Twenty six species of marine invertebrates belonging to phyla Porifera, Echinodermata, Coelenterata and Annelida collected from Goa, Maharashtra, Tamilnadu, Lakshadweep and the Andaman islands have been screened for antiviral, antibacterial, antifungal, antifertility and a wide range of pharmacological activities. Of the 26 extracts tested, 16 showed biological activity. Of the active extracts two showed hypotensive, six antiimplantation, two spasmogenic, and two diuretic activities.81 The species of Phylum Coelenterata which exhibited activity are: Gemmaria spp-I collected from Baga, Goa, exhibited hypotensive activity, LD50 1 87.5 (mg/kg, in mice), Gemmaria spp-II from Malvan, Maharashtra, was found very toxic, LD50 0.02 (mg/kg, in mice), Anthopleura panikkar from Anjuna, Goa also showed toxic properties, LD50 68.1 (mg/kg, in mice), Melitodes ornata from the Andaman Islands exhibited spasmolytic activity, Montipora divaricata from Mandapam, Tamilnadu, also showed spasmolytic activity, LD50 more than1000 (mg/kg, in mice); Pocillopora demicornis from Mandapam, Tamilnadu, exhibited hypotensive activity, LD50 68.1 (mg/kg, in mice). The extracts of corals that showed 100% antiimplantation activity in female mice are: Porites lichen from Malvan, Maharashtra, LD50 more than 1000 (mg/kg, in mice). Acropora corymbosa and Lobophyllia corymbosa both from Lakshadweep, and LD50 of both were more than 1000 (mg/kg, in mice) and Concinarea monile from Malvan, Maharashtra, LD50 more than 1000 (mg/kg, in mice) Porites lutea from Malvan, Maharashtra, exhibited 80% antiimplantation activity in female rats, LD50 more than 1000 (mg/kg, in mice). The species of the phylum Echinodermata which exhibited activity are: Astropecten spp. from Goa, showed spasmogenic activity, LD50 68.1 (mg/kg, in mice); Holothuria spp. (body-wall) from Goa, showed diuretic activity, LD50 15.63 (mg/kg, in mice); Holothuria spp. (Cuvierian glands) also from Goa, exhibited antiimplantation activity, LD50 1 5.63 (mg/kg, in mice). The species of phylum Porifera which showed activity are; Haliclona pigmentifera from Malvan, Maharashtra, exhibited diuretic activity, LD50 68.1 (mg/kg, in mice) and Suberites carnosus from Anjuna, Goa, showed spasmogenic activity, LD50 68.1 (mg/kg, in mice). It is interesting to note that the extract of Gemmaria spp., collected in the month of October, showed hypotensive activity. However, when the material was again collected in June, it was found devoid of activity. The results suggest that there are distinct seasonal variations in the activity. Holothurins from sea cucumbers have been found to be toxic to various animal species, including mammals. While confirming these results, the investigation unmasked their diuretic activity. The saponin fraction from sea cucumber Stichopus japonica has been reported to possess antifungal activity against Trichophyton asteroid and Candida albicans and other fungal species in vitro.82 This activity was, however, not observed in the species examined. Some of these saponins are also reported to have sperm immobilising properties and cause induction of egg and sperm shedding effects.83 The saponin fraction of the Cuvierian glands of the species showed antiimplantation activity. It is not possible to suggest the mechanism of this effect on the basis of available data. Extracts of sponges have been reported to show antibacterial and antifungal properties.84 But none of the species examined exhibited similar activity. The most promising activity observed was, perhaps, the antiimplantation activity found in five species of corals. Preliminary experiments conducted on mice have shown that these extracts were 100% active.

Twentyeight extracts of marine animals collected from the coasts of Goa, Maharashtra, Tamilnadu, Gujarat, Lakshadweep and the Andaman islands have been tested for antibacterial, antifungal, antiimplantation, antiviral, hypoglycaemic and a wide range of pharmacological activities. Of 28 extracts screened, 15 extracts showed biological activity. Of these two showed antiimplantation, three CNS stimulant, two hypotensive, four diuretic, four hypoglycaemic, two spasmolytic, one CNS depressant and one was found

toxic. Five extracts showed multiple activities.85 The species of phylum Coelenterata which exhibited activity are: Parazoanthus spp. collected from Kanya Kumari, Tamilnadu, in March showed hypoglycaemic and spasmolytic activities, LD50 more than 1000 (mg/kg, in mice) and Stoichactis giganteum collected from Okha, Gujarat, in March showed hypoglycaemic activity, LD50 68.1 (mg/kg, in mice). The species of phylum Echinodermata which showed activity are: Acanthaster planci collected from Kavaratti, Lakshadweep, in February exhibited antihistaminic and CNS stimulant activities, LD50 100 (mg/kg, in mice) and Astropecten indica collected from Ratnagiri, Maharashtra showed CNS depressant activity, LD50 6.81 (mg/kg, in mice). The species of phylum Mollusca which exhibited activity are Aplysia benedicti collected from Okha, Gujarat, in December showed hypoglycaemic activity, LD50 6.81 (mg/kg, in mice); Cellana radiata collected also from Okha, Gujarat, in December showed hypoglycaemic activity, LD50 1000 (mg/kg, in mice), Ischnochiton campus from Okha, Gujarat, in December showed antiimplantation activity, LD50 more than 1000 (mg/kg, in mice), Melibe rangi from Okha, Gujarat, in December exhibited CNS stimulant activity, LD50 178 (mg/kg, in mice) and Turbo intercostalis from Malvan, Maharashtra in October showed hypotensive activity, LD50 68.1 (mg/kg, in mice). The species of the phylum Porifera which showed activity are: Aurora globostellata collected from the Andaman island in February exhibited diuretic activity, LD50 more than 1000 (mg/kg, in mice); Axinella spp. also collected from Andaman in February showed diuretic activity, LD50 825 (mg/kg, in mice), Callyspongia spp. collected from Ratnagiri, Maharashtra, in October showed antiviral activity, LD50 681 (mg/kg, in mice); Dendrilla cactus collected from Anjuna, Goa, in February exhibited hypotensive and spasmolytic activities, LD50 more than 1000 (mg/kg, in mice); Dysidea fragilis also collected from Anjuna, Goa, in February also showed diuretic activity, LD50 more than 1000 (mg/kg, in mice) and Ircina ramosa collected from Malvan, Maharashtra, in February showed antiviral and CNS stimulant activities, LD50 1000 (mg/ kg, in mice). It is surprising that the sea cucumber Holothuria cinerascens did not show any toxicity. This might be due to the fact that the species is always found concealed underneath the boulders and are never exposed as other Holothurians sp. The most promising activity observed was the antiimplantation exhibited by Ischochiton camptus. Preliminary experiments conducted on mice have shown that the extract was 100% active. The occurrence of such activity in this species has not been reported hitherto.

Twentynine marine animals belonging to phyla Arthropoda, Coelenterata, Echinodermata, and Mollusca have been collected from the coasts of Goa, Maharashtra, Tamilnadu, Gujarat, Lakshadweep and the Andaman islands during the pre-monsoon and post-monsoon periods. The extracts of these marine animals have been tested for antibacterial, antifungal, antifertility, antiviral, hypoglycaemic and a wide range of pharmacological activities. Of the 29 extracts screened, 14 extracts showed activity. Of these two had the CNS stimulant, three hypoglycaemic, 26 antiimplantation, two antimicrobial, two antiviral, one spasmolytic, one hypotensive, one CNS depressant, activities. Six extracts were found toxic. Six of the active extracts showed multiple activities.86 The species of Arthropoda which showed activity is Leptodius arassimanus collected from Malvan, Maharashtra, in October. The extract of the animal showed CNS stimulant activity, LD50 31.6 (mg/kg, in mice). The species of Coelenterata which exhibited activity are: Echinomurica spp. collected from Grand island, Goa, in November showed antiimplantation activity, LD50 more than 1000 (mg/kg, in mice); Alcyonium spp. collected from Mandapam, Tamilnadu, in May showed antiviral activity LD50 more than 1000 (mg/kg, in mice), Epizoanthus spp. collected from Veraval, Gujarat, in December exhibited hypoglycaemic activity, LD50 0.38 (mg/kg, in mice) and Lexo suberites collected from Mandapam, Tamilnadu in February showed CNS depressant and hypoglycaemic activities, LD50 26.1 (mg/kg, in mice). The species of Echinodermata which showed activity are: Afrocucumis africana collected from Agati, Lakshadweep, in October showed antiviral and antiimplantation activities. LD50 681 (mg/kg, in mice), Actinopyga mauritiana collected from Lakshadweep in October showed hypotensive and antimicrobial activities LD50 2 1 5 (mg/kg, in mice), and Thelenata ananas collected from Lakshadweep showed antimicrobial activity, LD50 56.2 (mg/kg, in mice). The extracts of Holothuria ichinitis collected from Mandapam, Tamilnadu, in April and H. impotium collected from Lakashadweep in April were found toxic, LD50 26.1 and 38.3 (mg/kg, in mice) respectively. The species of Mollusca which showed activity are : Nerita spp. collected from Mandapam,

Tamilnadu, in January showed CNS stimulant activity, LD50 68.1 (mg/kg, in mice); Octopus vulgaris collected from Okha, Gujarat, in December exhibited spasmolytic activity, LD50 1000 (mg/kg, in mice) and Onchidium verruculatum collected from Mandapam, Tamilnadu, in May showed hypoglycaemic activity, LD50 more than 1000 (mg/kg, in mice). The ability of Octopi to paralyse prey before ingestion, with secretions of posterior salivary glands has long been known. The active agents present in the salivary glands of the Octopus have been found to be a mixture of low molecular weight amines, peptides, and proteinaceous materials.87 Ghiretti et al88 isolated an active proteinaceous fraction from the salivary glands of Octopus valgaris and O. macropus. While these authors found that the toxins from Octopi have paralytic and hypotension action, the investigations on Octopus vulgaris indicated only spasmolytic action.

Forty marine invertebrates belonging to the Mollusca, Coelentrata, Echinodermata and Porifera have been tested for antibacterial, antifungal, antiamoebic, antimalarial, antiviral, antifertility, hypoglycaemic and a wide range of pharmacological activities. Of these, three extracts each exhibited antiimplantation and hypoglycaemic activities; four were found toxic, five had antiviral activity against EMCV and or RDV, seven gave evidence of hypotensive activity, while nine extracts were found to be diuretic. One extract had the CNS stimulant effect, and one had oxytoxic activity as well as low order of abortifacient activity. Besides eight extracts revealed more than one type of activity.89 The species of Coelenterata which showed activity are: Acropora corymbosa collected from Kadmai Island, Lakshadweep, in January showed CVS activity, Acropora formica collected from the same locality showed diuretic activity, LD50 2.15 (mg/kg, in mice), Acropora humilis collected from the Kadmai Island, Lakshadweep, in January exhibited antiviral activity against Ranikhet Disease virus, LD50 more than 1000 (mg/kg, in mice), Alcyonaria spp. collected from the same locality exhibited diuretic, and hypoglycaemic, activities, LD50 3.16 (mg/kg, in mice); Montipora divaricata collected from Krusadai Island, Tamilnadu, in September showed hypoglycaemic activity, LD50 1000 (mg/kg, in mice), Paracondylacts spp. collected from Chandipur, Orissa, in April showed antiimplantation activity in rats, LD50 more than 1000 (mg/kg in mice); Zoanthus spp. collected from Veraval, Gujarat, in April showed cardiovascular effects. The species of Crustacean which showed activity is Eurythoe complanata collected from Chandipur in April showed diuretic activity. The species of Echinodermata which showed activity are: Pentaceraster regulus collected from Rameswarm, Tamilnadu, in September showed diuretic and antiviral activity against Encephalomyocaritis virus; Ischnochiton campus collected from Orissa in March exhibited antiimplantation activity in rats and CNS activity, LD50 26.1 (mg/kg, in mice); Modiolus striatulus collected from Krishnapuram, Orissa in February showed diuretic activity, Terebralia palustris, collected from South Andaman in April showed cardiovascular effects. The species of

Porifera which showed activity are: Axinella andamanensis collected from the Red Skin island, South Andaman, in April showed cardiovascular activity, LD50 46.4 (mg/kg, in mice), Callyspongia spinosissima collected from Rameswaram, Tamilnadu, in September showed antiviral activity against Ranikhet Disease virus and Encephalomyocarditis virus; Heteronema erecta from Red Skin island, South Andaman in September exhibited hypoglycaemic activity, Sigmadocia pumlla from Rameswaram, Tamilnadu, in September showed, diuretic, antiimplantation activity in rats and cardiovascular effect; Spirastrella inconstans from Krusadai island, Tamilnadu, in September exhibited diuretic activity, LD50 more than 1000 (mg/kg, in mice and Spirastrella inconstans var. digitata from Rameswarm, Tamilnadu, in September showed antiviral activity against Encephalomyocarditis virus.

Many Coelenterates produce toxins or other biologically active metabolites not only for self-defence but at times to capture prey. Echinoderms are known to contain polyhydroxysteroids and saponins. Most of these saponins are reported to have haemolytic activity. Mostly the secondary metabolites isolated from hard crust Molluscs are venomous in nature, and are used by the animals to capture prey. Sponges are by far the most extensively studied marine animals. A variety of biologically active constituents have been isolated from sponges.

Extracts of marine organisms have been assayed for their cardiovascular90 and toxic properties.91 The results of screening of 118 marine organisms (Coral, Alcyoniarians, Molluscs, Echinoderms) found in coastal waters of India, for their toxicity on fish and mice fingerlings as well as their hemolytic activities are reported.92 Echinoderms were found to be toxic to both fish and mice. They also exhibited high order of hemolytic activity. The Alcyoniarians were found toxic to fish and mice, but had weak hemolytic activity. The Molluscs, Patelia chathalamus, Trochus spp., Conus spp., Siganus spp. and Conus textile were found toxic to fish only, whereas Drupa heptogonalis was found lethal only to mice. The coral Acropora formosa and A. millepora exhibited hemolytic activity and were the only corals toxic to mice. Subergorgia suberosa, the only gorgonian collected showed lethal toxicity to fish as well as strong hemolytic activity. The sponges did not show toxic reaction to fish and mice, but exhibited weak hemolytic activity. Specimen of Spirastrella inconstans, Porites lutea, Pocillopora damicornis, Favites abdita, Montipora digitata and Noditittoria pyramidalis, collected from three different locations to determine whether their biotoxicity differs with change in ecological conditions, showed that their biotoxicities did not differ with ecological changes.

4.4 Search of Pharmaceutical^ Useful Compounds

Rinehert et al93 have been searching pharmaceutically useful compounds from marine organisms. Their first effort invovled a survey of marine organisms for antibacterial and antifungal properties. The bioassay were carried out on shipboard.94 These were the first systematic shipboard assay for pharmaceutical activity, and had many advantages.95,96 The most active antiviral extract in shipboard testing was from a tunicate identified as Eudistoma olivaceum,97 but the extract was surprisingly inactive in the secondary assay. However, the extract of the recollected sample proved very active in both primary and secondary assays against Herpes simplex and other viruses, confirming the value of on site assay. Chemical investigation of the bioactive extract of Eudistoma yielded 17 eudistomins having variously substituted P-carbolines.98,99 Although all the isolated compounds exhibited antimicrobial or antiviral activity, the most potent compounds were the tetracyclic eudistomins with the unique oxathiazepine ring. The in vivo testing of these compounds could not be carried out due to the scarcity of the tunicate and paucity of many of the eudistomins. Rinehart et al100,101 have synthesised a number of these eudistomins. However, oxathiazepine eudistomins have been prepared in extremely poor yield.

The extract of the tunicate Trididemnum solidum was found to have potent antiviral activity in bioassays carried out on shipboard.93 It was also found to be most cytotoxic. Moreover, these activities were confirmed in in vivo testing at Upjohn,101 USA. Nine major and several minor didemnins have been isolated from the extract of T. solidumW2~W4 which is widely distributed and didemnin-B was relatively abundant in it. Syntheses of some didemnins have been reported.105,106 Didemnins are active in vivo against DNA and RNA viruses. Of these, didemnin-B is the most active. Besides, didemnin-B exhibits remarkable immunosuppressant activity.107 It is 1000 times as potent as cyclosporin-A in inhibiting T-cell mitogenesis. It has also been shown in vivo activity in prolonging skin grafts.96 Unfortunately, didemnin-B is toxic.

Ecteinascidia turbinata is reported to contain a potent antitumour agent.108 An interesting immunoregulatory activity was subsequently observed in the extract of the organism.109 Later on, cytotoxicity was found in the extract. Counter current chromatography and TLC bioautography on tissue culture plates resulted in the isolation of ecteinascidins in yields 10-4 to 10-6 percent.96 All the compounds had either anti-bacterial activity or cytotoxicity against L 1210 leukemia cells.96

Over 300 marine organisms from Okinawan water have been screened for cytotoxicity, antiviral and antimicrobial activities.110 An extract of a sponge Theonella spp. was found highly cytotoxic in the assay against P 388 murine leukemia cells. Bioassay guided separation led to the isolation of an active constituent designated as misakinolide A, which had IC50 10 ng/ml in in vitro tests and T/C 145% at a dose of 0.5 mg/kg against P 388 in mice. The biology and ecology of tropical Holothurians have been reviewed.111 Work has been conducted on the toxicity of sponges and holothurians.112

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