Tea silkworm droppings as an enriched source of tea flavonoids

Abstract

Andraca droppings is the waste excreted from the tea biter Andraca theae. Its chemical constituents and potential medical use, unlike those of the traditional Chinese medicine silkworm droppings, have not been reported yet. To explore new nutraceuticals, the chemical constituents of this substance were investigated. Since the bioactive ingredients are generally present in the EtOAc-soluble fraction, this fraction, obtained from the ethanolic extract of the dried Andraca droppings by liquid-liquid partitioning, was separated by chromatographic methods, including Sephadex LH-20, centrifugal partition chromatography, and RP-18 columns, to produce 14 compounds (1-14). They were characterized as 1,7-dimethyl xanthine (1), three benzoic acids (2, 3, and 5), and 10 flavonoids (4, 6-14). The amount of compounds 6, 7, 10, 13, and 14 in the droppings were 1.7-15.5-fold compared to those of tea leaves. In addition, 1,7-dimethyl xanthine (1) was found present only in the Andraca droppings but absent in tea leaves. Therefore, except for compound 1, which might be transformed from caffeine by microflora in the insect, the compounds were believed not to be absorbed by the worm gut and excreted directly. The present study suggests the Andraca droppings are an enriched source of the bioactive flavonoids from tea leaves and are potential as a useful nutraceutical.

Keywords: 1,7-dimethyl xanthine; Andraca theae; droppings; flavonoids; metabolites.