Quality assessment and scavenging activity of Siamese neem flower extract

Abstract

Young 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 1178 mg% dry weight (average 772 mg%), and 1 to 10 mg% dry weight (average 5 mg%), respectively. EC₅₀ of the scavenging activity of all extracts was found in the range of 27–133 µg mL⁻¹. Loss on drying of the extracts was less than 7% w/w and no sign of toxicity (LD₅₀ > 5 g kg⁻¹) was found.

Keywords:

• Azadirachta indica
• Meliaceae
• quercetin
• rutin
• scavenging activity
• Siamese neem
• standardisation

Acknowledgements

This project was granted by The Thailand Research Fund with Office of Small and Medium Enterprises Promotion and also supported by The Office of the Higher Education Commission and Mahidol University under the National Research Universities Initiative. The authors thank Mr Panupon Khumsupan for his kind proofreading of this manuscript.