Frontiers in Natural Product Chemistry - Current Issue

Essential oil (0.51%) has been isolated from the rhizomes of Zingiber zerumbet from which a white crystalline fraction-A (m.p.62°C) has been separated and purified. Another fraction-B (m.p. 66°C) has been isolated from petroleum ether (40-60°C) extract. The fraction-A & B have been analyzed by, IR, GC/MS. From the above observation it appears that the major constituent of fraction-A & B is same and the structure is possibly 2,6,10- cycloundecatriene-1-one 2,6,9,9- tetramethyl.

Bioflavonoids were once known as vitamin P and are also considered semi-essential nutrients that are responsible for the color of fruits and flowers. They are used in the treatment or prevention of various diseases. There are four categories and these are the proanthocyanidins, quercetin, the citrus flavonoids and green tea polyphenols. The major sources of these bioflavonoids are from plants. The bioflavonoids are known for their antioxidant activity but a great number of other bioactivities are also attributed to them. Some of these bioactivities will be presented as well as the bioactivities of the rare flavonoids isolated from Syzygium samarangense (Blume) Merr. & L.M. Perry. Plant natural products, arguably, will still play a major role in providing the world with an alternative and a more effective health care.

In a continuation of our studies towards the discovery of biologically active compounds from Sri Lankan plants, recently we have chemically investigated the various parts of Diploclisia glaucescens (Menispermaceae), Filicium decipiens, Pometia eximia (Sapindaceae), Artocarpus nobilis (Moraceae) and Bridelia retusa (Euphorbiaceae). These work led to the isolation of a number of ecdysones, triterpenes, saponins, chalcones, stilbenes, flavonoids including over twenty-five new natural products. Some of these compounds showed high molluscicidal, insecticidal, antifungal activities and radical scavenging properties towards DPPH.

There are approximately 100 species of Zanthoxylum in the tropical and subtropical regions, and 10 of them are indigenous to Taiwan. For the last 10 years, our laboratory has examined six species of Zanthoxylum in Taiwan (Z. ailanthoides, Z. integrifoliolum , Z. nitidum, Z. pistaciiflorum , Z. schinifolium and Z. simulans) for their chemical and bioactive compounds. This research has led to the isolation of 59 new compounds and around 200 known compounds. The structures of the new compounds were established by spectroscopic data and chemical evidence. These new compounds showed diversity of structures including benzo[c]phenanthridine, 2-phenyl-1-N-methylphthaliamide, pyranoquinoline, 2-quinolone, isobutylamide, indolopyridoquinazoline, aporphine, phenylacetonitrile, coumarin, phenylpropanoid, lignan, and flavonoid. Several isolates showed antiplatelet aggregation activity in vitro.

Leaf, stem and root of Murraya paniculata (L.) Jack was extracted in four different organic solvents (petroleum ether, ethyl acetate, acetone and methanol). The extracts were tested on the mortality of adult male and female of Callosobruchus maculatus F. All the evaluated extract was toxic to both the sexes. Males generally showed higher susceptibility compared to females. Petroleum ether extract was more toxic than others. It was in the order: pet. ether>EtOAc>acetone>MeOH extract. Leaf extract was most toxic in comparison to stem and root extracts. It was in order: Leaf>root>stem. Generally, 72 hours exposure exhibited lower LD50 values compared to 24 and 48 hours.