Crystal Structures of Flavone <i>C</i>-Glycosides from Oolong Tea Leaves: Chafuroside A Dihydrate and Chafuroside B Monohydrate

Abstract

Chafuroside A and chafuroside B are flavone C-glycosides isolated from oolong tea leaves. They have a number of beneficial pharmacological activities related to antiinflammation at various concentrations. However, no crystallographic study of chafurosides has yet been reported. In the present study, the crystal structures of chafuroside A and chafuroside B were investigated using single-crystal X-ray diffraction. The asymmetric unit of the chafuroside A crystal consists of one chafuroside A and two water molecules, and that of chafuroside B contains one chafuroside B and one water molecule. The flavone moiety of chafuroside A is curved, i.e., the angle between the best-fit planes of the chromene and phenyl rings is 18.9°, whereas the chafuroside B flavone moiety is relatively flat. A comparison of the curvatures of the flavone moieties of various C-glycosides showed that the curvature of chafuroside A is significantly larger than those of the others. This structural feature might contribute to the differences between the strengths of the pharmacological activities of chafurosides A and B.

Therapeutic Potential of Controlled Delivery Systems in Asthma: Preclinical Development of Flavonoid-Based Treatments

“…They concluded that the transformation into nanocrystals improves the bioavailability and solubility of quercetin in water, in addition to reducing OVA-induced Th2 cytokines IL-4 and IL-5 levels, and IgE production, as well as attenuating the activation of mast cells, and improving the control for allergic asthma [ 149 ]. The flavone chafuroside A (C 21 H 18 O 9 ; Figure 3 ) is a flavone C-glycosides first isolated from oolong tea leaves, which possesses an unusual structural characteristic in the ether connection of C2″-hydroxyl group of the mannose and the aglycone compounds [ 150 ]. Structure–activity studies demonstrated that the flavone moiety of chafuroside A is curved, which may positively interfere in its pharmacological activities [ 150 ].…”

“…The flavone chafuroside A (C 21 H 18 O 9 ; Figure 3 ) is a flavone C-glycosides first isolated from oolong tea leaves, which possesses an unusual structural characteristic in the ether connection of C2″-hydroxyl group of the mannose and the aglycone compounds [ 150 ]. Structure–activity studies demonstrated that the flavone moiety of chafuroside A is curved, which may positively interfere in its pharmacological activities [ 150 ]. Chafuroside A was reported to be safe in mice models of colon cancer from 20 to 25 parts per million (p.p.m.)…”