투고논문

Spirostane-type steroidal saponin from Allium hookeri roots with mushroom tyrosinase inhibitory activity

Yun Na Kim¹, Jae Sun Lee¹, Kwang Ju Ock², and Eun Ju Jeong^1,*

¹Department of Agronomy and Medicinal Plant Resources, Gyeongnam National University of Science and Technology, Jinju 52725, Republic of Korea

²Max Bright Samchae, Jinju Industry Foundation, Munsan-eup, Jinju 52839, Republic of Korea

Received Nov 27, 2019; Accepted Dec 12, 2019

Abstract Allium hookeri (Liliaceae) has been received the increasing attention as a bioactive resource due to its potent biological activities including anti-oxidant, anti-obesity, anti-microbial and lipid-regulating activities. The beneficial effects of A. hookeri are known contributed from the high content of organosulfur compounds in A. hookeri. Though a variety of articles demonstrated that A. hookeri contains 'saponin' as a bioactive constituent, the scientific evidence to prove it was limited. In the present study, we have attempted to identify saponin contained in A. hookeri through chromatographic isolation and NMR spectroscopic methods. As a result, a spirostane-type steroidal saponin (1) has been successfully isolated from the methanolic extract of A. hookeri roots. The structure of 1 was elucidated by extensive 1D and 2D spectroscopic methods including ¹H-NMR, ¹³C-NMR, ¹H-¹H COSY, HSQC, HMBC and NOESY; identified as (3b, 22R, 25S)-spirost-5-en-3yl O-6-deoxy-α-L-mannopyranosyl-(1→4)-O-6-deoxy-α-L-mannopyranosyl-(1→4)-O-[6-deoxy-a-L-mannopyranosyl-(1→2)]-β-D-glucopyranoside. 1 showed the significant inhibitory activity on mushroom tyrosinase with IC₅₀ values of 248.7 mM while the inhibition on alpha-glucosidase was not significant.

Keywords Allium hookeri saponin constituent, alpha-glucosidase, mushroom tyrosinase, 1D and 2D NMR, spirosstanol oligoglycoside

* Address correspondence to: Eun Ju Jeong, Department of Agronomy and Medicinal Plant Resources, Gyeongnam National University of Science and Technology, Jinju 52725, Republic of Korea, Tel: +82-55-751-3224; E-mail: ejjeong@gntech.ac.kr