Photochemical Reaction of ihydroartemisinin esters

Photochemical reaction of three dihydroartemisinin esters: acetate, benzoate and succinate under 254 nm UV light in CH2Cl2 have been studied. The result showed, that these artemisinin derivatives are easily decomposed forming different elimination and rearrangement compounds

Distributed Orientation Localization of Multi-agent Systems in 3-dimensional Space with Direction-only Measurements

When a group of agents such as unmanned aerial vehicles are operating in 3-dimensional space, their coordinated action in pursuit of some group objective generally requires all agents to share a common coordinate frame or orientations of the coordinate axes of agents up to an unknown coordinate rotation common to all agents, which are simply referred to as having common coordinate axis orientations. Given coordinate axes that are initially unaligned, this paper considers the process of using direction measurements between agent pairs (obtained in their own coordinate frames) to achieve orientation localization, i.e. determination of common coordinate axis orientations, the calculations all being distributed. The process builds on the initial determination of relative orientations of agent pairs in a common coordinate basis. Distributed differential equations then allow determination of a common set of coordinate axis orientations, uniquely up to a common rotation transformation, which can itself be determined if and only if one or more agents have access to global coordinates.This work was supported, in part, by the National Research Foundation (NRF) of Korea under the grants NRF2016M1B3A1A01937575 and NRF-2017R1A2B3007034, and in part, by the Australian Research Council under grants DP-130103610 and DP-160104500, and Data61-CSIRO

Triterpene from the roots of Codonopsis pilosula.

From the roots of Codonopsis pilosula (Franch) Nannf (Campanulaceae) five triterpenoids: taraxerol, taraxeryl acetate, 14-a-taraxeran-3-one and D:B-friedoolean-5-ene-3-b-ol as well as a-spinasterone were isolated. Their structures have been identified by MS, 1H-, 13C-NMR spectroscopy and comparison with reported data

Synthesis of acyclovir as an antiherpes-virus drug

A one-pot process for high-yield regioselective synthesis of 9-[(2-hydroxyethoxy) methyl]guanine (acyclovir),  an antiherpetic agent, was achieved from guanine via the steps of reacting of N2,N9 -diprotected guanine with 1-acetyl-2-acetylmethoxy-ethyleneglycol in presence of phosphoric acid or polyphosphoric acid. Total yield of product was 59%. The obtained acyclovir meets the standards in the British Pharmacopoeia 2007 (BP2007). Its activity as inhibitor of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) was evaluated according to the plaque reduction assay method and compared with the standard compound. The synthesized acyclovir showed a similar activity as the control. Keywords: Acyclovir, Herpes simplex virus, Nucleoside, One- pot synthesis

Screening for the main triterpenic acids in Centella asiatica samples from North and South of Vietnam

The optimal conditions for extraction, hydrolyzation and quantitative determination of the total amounts of two main triterpene acids, asiatic acid, and madecassic acid in Centella asiatica by HPLC and column chromatography are described. Using this method the asiatic acid and madecassic acid content of three Centella asiatica samples collected in Sontay City, Namdinh province, and in Ho Chi Minh City have been screened. The result showed that the contents of both triterpenic acids are higher in Sontay sample and in each sample the content of madecassic acid is higher than that of asiatic acid. Keywords. Centella asiatica, asiatic acid, madecassic acid, quantification

flavonoids from Fissistigma acuminatissima

From the leaves of Fissistigma acuminatissima growing in Vietnam, two flavonoids, catechin and isorhamnetin-3-o-rutinoside were isolated. Their structures were characterized on the basis of MS and NMR spectra data and comparison with reported data.Keywords: Annonaeae; Fissistigma acuminatissima; catechin; isorhamnetin-3-o-rutinoside

Abietane diterpenoids and neolignans from the roots of Pinus kesiya

The phytochemical investigation of the ethyl acetate extract of Pinus kesiya Royle ex Gordon roots led to the isolation of two abietane diterpenes, 7-oxo-15-hydroxy-dehydroabietic acid (1) and dehydroabietic acid (2) as well as two neolignans, cedrusin (3) and cedrusin-4-O-β-D-glucopyranoside (4). Their structures were determined by combination of spectral analysis and comparison with reported data. Among them, compound 1 was isolated from the genus Pinus for the first time. Keywords. Pinus kesiya, abietane diterpenes, neolignans, dehydroabietic acid, cedrusin