7- and 8-O-methylherbacetin-3-O-sophorosides from bee pollens and some structure activity observations

A new flavonol glycoside, 7-O-methylherbacetin-3-O-sophoroside, has been characterized from Ranuncuhs sardous pollen, 8-O-methylherbacetin-3-O-sophoroside from Ulex europaeus pollen and 8-O-methylherbacetin 8-O-glucoside from Raphanus raphanistrum pollen; all pollens were obtained from bee pollen. It is demonstrated that the unusual UV-visible absorption spectra of 7- and 8-O-methylherbacetin 3-O-glycosides can be used conveniently to distinguish these and their aglycones. The distribution of various flavonol glycosides in pollen is discussed in terms of its significance to the previously established role of flavonols in pollen germination. No evidence for taxa specificity of individual flavonol glycosides was found; however, a case is made for elevating the significance of flavonol glycosides, particularly the 2 ''-O-glycosides of flavonol-3-O-glycosides in stimulating pollen tube growth. Copyright (C) 1996 Elsevier Science Ltd