Insights on the influence of microwave irradiation on the extraction of flavonoids from Terminalia chebula

• Flavonoid extraction from T. chebula enhanced by microwave irradiation.
• Solid-liquid equilibrium data altered favourably by microwave irradiation.
• Temperature extraction coefficient improved at higher solvent-to-feed ratios.
• Higher yield at lower solvent & energy consumption using short-duration MAE.

The aqueous extract of Terminalia chebula Retz. plays an important role in traditional medicinal formulations. Experiments on microwave irradiation during aqueous extraction of flavonoids from T. chebula reveal the influence of microwaves on solid-liquid equilibrium, leading to higher equilibrium flavonoid concentration in the liquid phase at a fixed flavonoid concentration in the solid phase. As a result, microwave assisted extraction (MAE) provided 14.17% enhancement in equilibrium yield, compared to that obtained in conventional extraction at a temperature of 100 °C and a solvent-to-feed ratio of 40 mL/g. The effective diffusion coefficient at 40 mL/g increased from 0.68 × 10−11 to 1.31 × 10−11 m2/s due to microwave irradiation. Our data conclusively indicates that microwave assisted extraction provides higher yield, equilibrium concentration and effective diffusion coefficient. The study has also revealed the possibility of utilization of MAE for short duration extraction with lower solvent and energy consumption. The extractions were found to be endothermic and spontaneous, with the spontaneity improved due to microwave irradiation.

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