The establishment of efficient bioconversion, extraction, and isolation processes for the production of phyllodulcin, a potential high intensity sweetener, from sweet hydrangea leaves (Hydrangea macrophylla Thunbergii).

Hydrangea leaf tea has been traditionally consumed in the far-east Asian countries and is favoured for its distinct minty-sweet taste. Phyllodulcin is identified as a key sweet-tasting compound; it is 400-800 times sweeter than sucrose. However, its extraction has not been well-documented. In an effort to optimise phyllodulcin production, pretreatment processes to accumulate phyllodulcin as a final metabolite in leaf tissue were studied, and an efficient process was established for the extraction and purification of phyllodulcin.Phyllodulcin was structurally identified using an LC/MS system. Hydrangea leaves were processed by either hand rolling or mechanical blending, by exposing them at different drying temperatures (25 and 70°C), and even by inducing bioconversion in leaf tissue. The leaf powder was extracted with various solvents (methanol, ethanol, and water) by soaking at 25°C for 12 h, ultrasonication at 35°C for 1 h or accelerated solvent extraction (ASE). Extracts were purified with ion exchange resins and purified using preparative HPLC.Traditional hand rolling and drying at 70°C significantly increased phyllodulcin accumulation in the leaves. Meanwhile, more phyllodulcin was obtained from the leaves blended mechanically or converted enzymatically compared to traditionally processed ones (P < 0.05). Methanol and ethanol were superior to water as extraction media, and the greatest phyllodulcin yields obtained by ASE, soaking and ultrasonication were 21.28, 21.20 and 19.33 mg/g, respectively, when methanol was used. Highly pure phyllodulcin powder was obtained with a yield of 2.12%.This promising result would be beneficial to the industrial utilisation of phyllodulcin as a potential high-intensity sweetener.