Quercetin and rutin contents in Siamese neem flower extracts prepared by different extraction methods

Abstract

Siamese neem tree (Azadirachta indica A. Juss. var. siamensis Valeton) is a medicinal plant found in every part of Thailand. The young flowers of this plant are commonly consumed with sweet sauce as a bitter tonic vegetable for elemental tonic purpose [1]. The flower extract has been reported to exhibit in vitro free radical scavenging activity and inhibit lipid peroxidation of bronchogenic cancer cell line [2]. Active components in Siamese neem flowers are flavonoids such as quercetin and rutin. The content of these compounds in the crude extract is depended on the method of extraction. This work investigated the quantity of rutin and quercetin in the flower extracts of Siamese neem tree prepared by several extracting methods using high performance liquid chromatography (HPLC) to find the appropriate extraction method which gives the maximum contents of rutin and quercetin. The flowers were extracted using maceration, percolation, decoction, soxhlet extraction, ultrasonic extraction (UE) and microwave assisted extraction methods. The solvent used in maceration, percolation and soxhlet extraction was 50% ethanol, in decoction and MA was distilled water, while in UE was both 50% ethanol and distilled water. By HPLC, the results showed that soxhlet extraction method gave the extract containing the maximum contents of rutin and quercetin (10.21 and 0.12% w/w of the extract, respectively). Quercetin was detected only in the extract prepared using 50% ethanol as the solvent. Thus, soxhlet extraction should be the appropriate extraction method for Siamese neem flowers to yield the extract with high contents of active components, rutin and quercetin.