Systematic HPLC/DAD/MSn study on the extraction efficiency of polyphenols from black goji: Citric and ascorbic acid as alternative acid components in the extraction mixture

BACKGROUND: The beneficial effects of the fruit of Lycium rhutenicum (black goji) have been linked to their polyphenolic profile. OBJECTIVE: Systematic examination of the extraction efficiency of polyphenols from cultivated black goji from Macedonia was carried out using 25 different solvent mixtures containing methanol, acetone or water combined with different acids (hydrochloric, acetic, citric and ascorbic acid). METHODS: An HPLC/DAD/MSn method was used for identification and quantification of phenolic acids, flavonoids, anthocyanins and also spermines and spermidines. RESULTS: The extraction solvent composition was found to have a significant effect on the yield of total as well as specific polyphenols. Pure methanol was found to be more efficient solvent for extraction of total phenolic compounds than pure water or acetone. Ascorbic acid in methanol (2%, m/v) was found to be the most efficient extraction solvent for total phenolic compounds. Aqueous solutions of citric and ascorbic acid gave the highest yield of phenolic acids, spermidines and flavonoids. The anthocyanin content in these extracts was somewhat lower in comparison with the one obtained with methanol/water/ascorbic acid (70 : 28 : 2). The qualitative analysis of the fruits cultivated in Macedonia showed similar polyphenolic pattern and anthocyanin content to the native plant growing in China. CONCLUSIONS: Citric and ascorbic acid can be used as alternative acid components in the extraction mixture.

Automated summary

The extraction efficiency of polyphenols from black goji fruit was significantly influenced by different solvent mixtures, with pure methanol being the most efficient. The addition of ascorbic acid as an extraction solvent additive can enhance the yield of polyphenols, while aqueous solutions of citric and ascorbic acid showed the best extraction results.