Worarat ChaisawangwongWandee GritsanapanMahidol University2018-10-192018-10-192013-03-25Natural Product Research. Vol.27, No.4-5 (2013), 394-40114786427147864192-s2.0-84875130137https://repository.li.mahidol.ac.th/handle/20.500.14594/31050Young leaves and flowers of Siamese neem tree (Azadirachta indica A. Juss. var. siamensis Valeton) are commonly consumed as a bitter tonic vegetable. Active antioxidant components in the flowers are rutin and quercetin flavonoids. The aqueous extracts of young flowers collected from 14 different locations in Thailand were quantitatively analysed using high-performance liquid chromatography for the contents of rutin and quercetin, and were determined for the loss on drying, heavy metals and pesticide residues, microbial contamination, solubility, chromatographic fingerprints and acute toxicity. The extracts contained rutin and quercetin in the ranges from 388 to 1178mg% dry weight (average 772 mg%), and 1 to 10mg% dry weight (average 5 mg%), respectively. EC50 of the scavenging activity of all extracts was found in the range of 27-133 mgmL-1. Loss on drying of the extracts was less than 7% w/w and no sign of toxicity (LD5045 g kg-1) was found. © 2013 Taylor and Francis.Mahidol UniversityAgricultural and Biological SciencesBiochemistry, Genetics and Molecular BiologyChemistryArticleSCOPUS10.1080/14786419.2012.706295