A new bis-indole, caulersin (4), was isolated from the alga Caulerpa serrulata, collected from the Xisha Islands in the South China Sea. The structure was established by spectroscopic methods.

Two new flavonoids, acanthophorin A (1) and acanthophorin B ( 2 ) , along with three known compounds tilimside (31, (-)-catechin (4) and quercetin (5) were Isdated from the red alga A~rmthophom spi&ena. "he structures of 1 and 2 were determined to be kaempferol 3-O-a-L-Tucopyranoside (1) and quercetin IO-a-L-fumpyrardde ( 2 ) by spectraq i c methods. Both l and 2 showed significant antioxidant activity.

[structure: see text] A new hemiketal steroid, named cladiellin A (1), was first isolated from the soft coral Cladiella sp. Its structure was determined by spectroscopic methods and X-ray analysis. Compound 1 easily converted to 1a when NMR spectra were measured in CDCl(3) solution and quickly changed to 1b when pyridine was used. The structures of dehydrated products 1a and 1b were determined by spectroscopic analysis. Bioassay showed that all these three compounds showed antioxidant activity.

A novel lanostanoid lactone (1) was f d isdated from the Alga Hypnea cenicorniS collected from the Xisha Islands in the South China Sea. The structure of 1 was determined on spectral evidence 8s 5a-lansta-8-erk3p, 22<-dihydroxy-22 ( R ) , 24 (S)-lactofie.Fhject supported by the State Key b r a t o r y of

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