Natural deep eutectic solvents: A paradigm of stability and permeability in the design of new ingredients

Vitamin C is a workhorse in food and cosmetics—but it's fragile. Could a new class of green solvents finally keep it stable and skin-permeable?

Ascorbic acid—vitamin C—is a vital ingredient in food and cosmetics, prized for its antioxidant power. But it degrades quickly, challenging formulators. Enter Natural Deep Eutectic Solvents (NADES), a novel class of green solvents with promising physicochemical properties for stabilizing bioactives.

In this study, researchers characterized various NADES, simulated vitamin C solubility using COSMO-Therm software, and measured antioxidant capacity via TEAC, DPPH, and ORAC assays. They tracked degradation over 30 days at two temperatures and assessed membrane permeability using the PAMPA method.

Key findings: organic acid-based NADES were more polar than sugar or polyalcohol-based ones. Lower pH increased degradation, but at 4°C, half-life was longer—with choline chloride:xylose performing best. However, betaine:malic acid, choline chloride:tartaric acid, and choline chloride:lactic acid stabilized worse than the control.

For permeability, lactic acid:glucose showed the highest permeability coefficient for both gastrointestinal (Log Pe: -4.99) and skin (Log Pe: -4.78), while malic acid:glucose had the lowest (-6.9). Not all NADES are equal—some protect vitamin C, hinting at broader applications for other bioactives.

Key Points

• Organic acid NADES are more polar than sugar or polyalcohol ones.
• Choline chloride:xylose best stabilized vitamin C at 4°C.
• Lactic acid:glucose showed highest permeability for GI and skin.