Flavonoids from silkworm droppings and their promotional activities on heme oxygenase-1

Abstract

A new flavane glucoside, 7,2′-dihydroxy-8-hydroxyethyl-4′-methoxyflavane-2′-O-β-d-glucopyranoside (3), along with three known flavonoids, 7,2′-dihydroxy-8-prenyl-4′-methoxyflavane (1), euchrenone a₇ (2), and 7,2′-dihydroxy-8-prenyl-4′-methoxy-2′-O-β-d-glucopyranosylflavane (4), was isolated from silkworm droppings. The structures of the compounds were elucidated on the basis of 1D and 2D NMR spectroscopic analyses and optical rotational characteristics. The compounds isolated from silkworm droppings were evaluated for their effects on heme oxygenase-1 (HO-1) activity. Compounds 1 and 3 increased the expression of HO-1 in HepG2 cells. HO-1 is an antioxidant enzyme that catabolizes heme to carbon monoxide, free iron, and biliverdin, all of which are involved in the suppression of inflammatory mediators.

Keywords:

• Bombyx mori
• 7,2′-dihydroxy-8-hydroxyethyl-4′-methoxyflavane-2′-O-β-d-glucopyranoside
• HO-1
• silkworm droppings

Acknowledgements

This study was supported by the Mental Health Food Development Program from the Korea Food Research Institute (20100797U0054101S000100) and the Development Program from the Agricultural Research & Development Promotion Center (108056033HD110).