A new HPLC–UV method for the quantification of terpenoids and antioxidant activity of commercial loquat leaf tea and preparation

Abstract

A number of recent studies on the loquat (Eriobotrya japonica Lindl.) leaf have demonstrated that loquat leaf extracts exhibited a wide range of pharmacological activities including hypoglycemic, anti-inflammatory, anti-tumor, neuroprotective and enhancement of brain health and liver function in the in vitro and animal models. Consequently, loquat leaf teas and dietary supplements are produced for human consumption. The aim of the present study was to develop a simple HPLC–UV method that can be used to simultaneously quantitate six triterpene acids and two sesquiterpene glycosides in commercial loquat leaf preparations including tea, granule and syrup, and to evaluate their total phenolic content and antioxidant activity. Total concentration of terpenes in six commercial products varied from 0.8 µg/mL to 14.8 mg/g, total phenolic content from 0.9 to 45.6 mg gallic acid equivalent/g, and antioxidant activity from 6.4 to 607.0 µmol trolox equivalent/g. The antioxidant activity correlated to total phenolic content significantly. The present study provided much needed information on the quality and content variability, and the potential of these products for future scientific investigations in human health.