Caulerchlorin, a Novel Chlorinated Bisindole Alkaloid with Antifungal Activity from the Chinese Green Alga Caulerpa racemosa

Caulerchlorin (2), a novel chlorinated bisindole alkaloid with an eight-membered cyclic ring between two indole rings incorporated directly with a chlorine atom, together with three known related metabolites, caulerpin (3), monomethyl caulerpinate (4), and caulersin (5), has been isolated from the Chinese green alga Caulerpa racemosa (Forssk.)J. Agardh.The structure of 2 was determined on the basis of extensive spectroscopic analysis.Compounds 2-5 were evaluated for their antifungal activity against Candida albicans (SC5314), Candida albicans (Y0109), Candida parapsilosis (ATCC 22019), Candida glabrata (537), Microsporum gypseum (Cmccfmza), Trichophyton rubrum (Cmccftla), Aspergillus fumigatus (07544), and Cryptococcus neoformans (32609), and the result showed that only compounds 2 and 4 had a moderate/weak antifungal activity against Cryptococcus neoformans (32609) with MIC 80 values of 16 and 64 g mL -1 , respectively.Indole alkaloids comprise a class of biologically active natural products biosynthesized by diverse range of organisms from both terrestrial and marine habitats.Within the marine environment, numerous indole alkaloids have been reported from sponges, 1 bryozoans, 2 coelenterates, 3 green algae 4 and red algae. 5ding to their interest is the fact that some of these metabolites display potent and diverse bioactivities, such as cytotoxic, 6 antifungal, 7 antibacterial, 7 antioxidant, 8 anti-inflammatory, 9 and antitumor properties. 10een algae of the genus Caulerpa are well-known as a rich source of indole alkaloids.Caulerpin (3), the first bisindole pigment from the genus Caulerpa, whose structure was first proposed in 1970 11 and later