A new enzyme assay method for screening a-glucosidase inhibitors with rapidity and simplicity was developed. The enzyme-substituted a-glucosidases for this assay was glucoamylase. Samples were spotted or developed on the silica gel plate. The agar solution containing substrate was poured on the plate, and paper impregnated with enzyme was layered on the agar. After incubation, an inhibitory circle would appear around the inhibitor. By using this method, more than 200 strains of marine microorganisms were screened. Among them, three active strains were found to secrete inhibitors in the culture medium.

Twenty-nine marine bacterial strains were isolated from the sponge Hymeniacidon perleve at Nanji island, and antimicrobial screening showed that eight strains inhibited the growth of terrestrial microorganisms. The strain NJ6-3-1 with wide antimicrobial spectrum was identified as Pseudoalteromonas piscicida based on its 16S Rrna sequence analysis. The major antimicrobial metabolite, isolated through bioassay-guide fractionation of TLC bioautography overlay assay, was identified as norharman (a beta-carboline alkaloid) by EI-MS and NMR.

ng seven tumor cell lines. Selective inhibition of K562 and HT-29 cells was observed from a methanolic extract in the range of 16-125 μg/mL. Radicalscavenging activity was greatest in an extract composed primarily of flavonol glycosides. Seven flavonol glycosides were isolated and purified from whole fruit for further evaluation; the anthocyanin cyanidin 3-galactoside was also purified for comparison with the flavonoids. Three flavonol monoglycosides were newly identified by 13C NMR as myricetin 3-α-arabinofuranoside, quercetin 3-xyloside, and 3-methoxyquercetin 3-β-galactoside (isorhamnetin); the other four isolated were the previously identified myricetin 3-β-galactoside, quercetin 3-β-galactoside, quercetin 3-α-arabinofuranoside, and quercetin 3-α-rhamnopyranoside. These compounds were evaluated for 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity and ability to inhibit low-density lipoprotein oxidation in vitro. Most of the flavonol glycosides showed antioxidant activity comparable or superior to that of vitamin E; cyanidin 3-galactoside showed activity superior to that of the flavonoids as well as vitamin E or Trolox in both antioxidant assays.

Five caffeic acid derivatives were found in the roots of yacon, Smallanthus sonchifolius (Poepp. And Endl.) H. Robinson, Asteraceae, as the major water-soluble phenolic compounds. The structures of these compounds were determined by analysis of spectroscopic data. Two of these were chlorogenic acid (3-caffeoylquinic acid) and 3,5-dicaffeoylquinic acid, common phenolic compounds in plants of the family Asteraceae. Three were esters of caffeic acid with the hydroxy groups of aldaric acid, derived from hexose. The structure of the aldaric moiety was determined by hydrolysis and comparison of NMR spectra with those of standard aldaric acids. The compounds were novel caffeic acid esters of altraric acid: 2,4-or 3,5-dicaffeoylaltraric acid, 2,5-dicaffeoylaltraric acid, and 2,3,5-or 2,4,5- tricaffeoylaltraric acid.

Yacon, Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson, Asteraceae, an important economic species grown for its juicy tuberous root, is potentially beneficial in the diet to diabetics. The antioxidative activity of yacon root was studied by 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Antioxidants were extracted by methanol and isolated and purified by gel permeation chromatography and preparative reverse-phase HPLC. Two of the major antioxidants were identified as chlorogenic acid and tryptophan by NMR and mass spectrometry.