Isolation of flavonoids from onion skins and their effects on K562 cell viability

Guo-Qing Shi,Jing Yang,Jiang Liu,Sheng-Nan Liu,Wen-En Zhao,Han-Xue Song,Yan-Qi Liu

doi:10.3329/bjp.v11is1.26419

Abstract

To investigate the anti-proliferative activity of flavonoids from onion skins, extraction by 50% ethanol (v/v), soxhlet polar fractionation, pH gradient separation, thin-layer chromatography, and recrystallization methods were used to isolate and purify flavonoids from dry onion skins. Anti-proliferative activities of some flavonoids obtained on leukemia K562 cell line were deter-mined by MTT assay. Results showed that flavonoids of onion skins were mainly in form of quercetin, kaempferol, isorhamnetin, apigenin-7-O-?-D-glucopyranoside, quercetin-3-O-?-D-glucopyranoside, kaempferol-7-O-?-D-glucopyranoside and rutin. Quercetin and kaempferol decreased K562 cell viability, and quercetin had stronger effect. However, isorhamnetin and rutin exhibited certain proliferation-promoting effects. It suggests that ortho hydroxyl groups on B ring of onion flavonoids might be the key structural elements of their cytotoxic effects on K562 cells, and hydroxyl groups in position 3 or carbonyl groups in position 4 might be one of the structural effect elements.

Highlights

Onion (Allium cepa L.) is considered to be one of the world’s oldest cultivated vegetable, and contains high level of dietary flavonoids (Slimestad et al, 2007), which are present in much higher concentrations in the onion skin than they are in the fleshy bulb (Kim and Kim, 2006; Yao et al, 2004; Sellappan and Akoh, 2002)
The Fourier transform infrared (FT-IR) spectrum (Nexus470 Fourier transform infrared spectrometer, Nicolet Instrument Company, USA) spectrum of compound 1 contained a broad peak at 3238 cm-1, as well as a much narrower C-O peak in the range of 1250–1050 cm-1, which were consistent with the presence of hydroxyl groups
FT-IR analysis revealed peaks at 3318 and 1250–1050 cm-1, which were consistent with the presence of hydroxyl groups

Summary

Introduction

Onion (Allium cepa L.) is considered to be one of the world’s oldest cultivated vegetable, and contains high level of dietary flavonoids (Slimestad et al, 2007), which are present in much higher concentrations in the onion skin than they are in the fleshy bulb (Kim and Kim, 2006; Yao et al, 2004; Sellappan and Akoh, 2002). This paper was presented in the 3rd International Conference on Biomedicine and Pharmaceutics in Zhuhai, China, on December 11-13, 2015. Their structures, because flavonoids with different structures exhibit a variety of different biological activities (Kefalas et al, 2006). The isolation and identification of flavonoids from onion skin would enhance our understanding of the material basis for their biological activities, but could provide a theoretical basis for the utilization of these compounds in a number of other areas of research. Significant research efforts have been directed towards the characterization of onion and onion skin flavonoids during the last decade (Soltoft et al, 2009; PérezGregorio et al, 2010; Kiassos, et al, 2009; Jin, et al, 2011) which has led to a significant increase in our understanding of these compounds.

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Results

Conclusion