The O-glycosides are surprisingly not often reported as aloe constituents although they occur in several other plants. Aloe-emodin-O-galactoside and aloe-emodin-11-O-rhamnoside were observed on leaf exudate chromatograms (reviewed Reynolds, 1985). More recently, 7-O-glucosylnataloe-emodin was isolated from A. nyerienis Christian ex I.Verd. (Conner etal, 1987) and 11-O-rhamnosyl aloe-emodin from A. rabaiensis Rendle (Conner etal, 1989). The 1-O-glucoside of homonataloin B has been characterized from A. lutescens Groenew.A (Van Heerden etal, 2002) and identified in a further 13 species (Viljoen etal, 2002), while a diglycoside of O-methoxy-nataloe-emodin-8-methyl ether has been previously described from A. vera.
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