Tigliane-Type Diterpene Esters from the Fruits of Shirakiopsis indica and Their Anti-HIV Activity

Four new diterpene esters, shirakindicans A-D (1-4), along with eight related known diterpene esters (5-12), were isolated from the fruits of the Bangladeshi medicinal plant Shirakiopsis indica. The structures of 1-4 were elucidated by spectroscopic data analysis and electronic circular dichroism (ECD) calculations. Shirakindican A (1) was assigned as a tigliane-type diterpene ester possessing an unusual 6β-hydroxy-1,7-dien-3-one structure, while shirakindican B (2) exhibits a tiglia-1,5-dien-3,7-dione structure. The anti-HIV activities of the isolated diterpene esters were evaluated and showed significant activities for sapintoxins A (5) and D (11), with EC₅₀ values of 0.0074 and 0.044 μM, respectively, and TI values of 1 100 and 5 290. Sapatoxin A (12) also exhibited anti-HIV activity with an EC₅₀ value of 0.13 μM and a TI value of 161.

Phytochemical studies on traditional herbal medicines based on the ethnopharmacological information obtained by field studies

Traditional herbal medicines, which have been used in the matured traditional medical systems as well as those have been used in ethnic medical systems, are invaluable resources of drug seeds. Ethnobotanical and ethnopharmacological survey may provide useful information of these herbal medicines, which are valuable for searching new bioactive molecules. From this viewpoint, we have been performing the ethnobotanical and ethnopharmacological field studies in Yunnan Province and Guangxi Zhuang Autonomous Region, China, and Mongolia. Phytochemical studies on traditional herbal medicines were performed based on the information obtained by our ethnobotanical survey. Herbal medicines used in Uzbekistan and Bangladesh were also investigated on the basis of the ethnopharmacological information obtained from collaborative researchers in the respective regions. Some studies were carried out for searching active substance(s) based on bioassay-guided fractionation and isolation. Over 150 new molecules were isolated in these studies, and their various biological activities were also demonstrated. This review summarizes the results of phytochemical studies of those traditional herbal medicines as well as biological activities of the isolated molecules.

OcUGT1-Catalyzed Glucosylation of Sulfuretin Yields Ten Glucosides

Sulfuretin glucosides are important sources of innovative drugs. However, few glucosides of sulfuretin have been observed in nature. Therefore, it is urgent to diversify sulfuretin glycosides. Herein, glycosyltransferase (GT)-catalyzed glycodiversification of sulfuretin was achieved. Specifically, a flavonoid GT designated as OcUGT1 was used as a biocatalyst for the glucosylation of sulfuretin with UDP-Glc. The OcUGT1-assisted glucosylation of sulfuretin yielded ten glycosylated products, including three monoglucosides, five diglucosides and two triglucosides. The three monoglucosides were thus identified to be sulfuretin 3′-, 4′- and 6-glucoside according to HR-ESI-TOFMS data and their coelution with respective standards. A major diglucoside was assigned as sulfuretin 4′,6-diglucoside by HR-ESI-TOFMS in conjunction with NMR analysis. The exact structure of the other four diglucosides was not well characterized due to their trace amount. However, they were reasonably inferred as sulfuretin 3′,6-diglucoside, sulfuretin 3′,4′-diglucoside and two disaccharide glucosides. In addition, the structural identification of the remaining two triglucosides was not performed because of their small amount. However, one of the triglucosides was deduced to be sulfuretin 3′,4′,6-triglucoside based on the catalytic behavior of OcUGT1. Of the ten sulfuretin glucosides, at least six were new compounds. This is the first time to obtain monoglucosides, diglucosides and triglucosides of sulfuretin simultaneously by a single glycosyltransferase.

Occurrences, biosynthesis and properties of aurones as high-end evolutionary products

Recent years have witnessed a considerable renewed interest for the uncommon flavonoid class of aurones. The characterization of two major biosynthetic machineries involved in their biosynthesis in flowers has encouraged the revival of phytochemical studies and identification of original structures, a process started almost seventy-five years ago. This review draws up an exhaustive map of natural occurrences of aurones their biosynthetic pathways and roles, with the aim to link their original structural properties among flavonoids to their place in evolution and the selective advantages they bring to some of the most advanced taxa in the plant kingdom.