Stability indicating RP-HPLC method for the simultaneous determination of multi-flavonoid compounds in herbal extracts, besides green analytics

A stability-indicating RP-HPLC method was developed and validated for the simultaneous quantification of five flavonoids, <i>viz.</i>, epigallocatechin gallate (EGCG), silibinin (SL), naringenin (NG), genistein (GT), and apigenin (AG), in herbal extracts. Chromatographic separation was achieved on a C18 column using 0.1 M ammonium acetate and methanol at 40:60% v/v. The method demonstrated acceptable resolution, linearity (<i>r</i>²: 0.9905-0.9969), precision (<2% RSD), recovery (82.09-99.62%), and sensitivity (LOD: 0.068-1.516 μg/mL; LOQ: 0.20-4.59 μg/mL). The method successfully quantified these flavonoids in the aqueous extracts of <i>Phyllanthus emblica</i> L., <i>Brassica oleracea L.</i>, <i>Camellia sinensis (L.). Kuntze</i>, <i>Moringa oleifera L.</i>, <i>Syzygium cumini (L.) Skeels,</i> and <i>Allium cepa L.</i> Results revealed that EGCG was the major constituent found in all extracts, whilst AG, GT, and SL were found as minor constituents. The method identified six degradation products with a mass balance of >98%. The method demonstrated acceptable green chemistry by the AGREES and GAPI tools.