Phytosomes For Improving the Bioavailability and Antidiabetic Activity of Herbal Medicine: A Review

Introduction: Diabetes mellitus represents a long-term metabolic disorder marked by sustained elevation of blood glucose levels owing to inadequate insulin secretion, impaired insulin sensitivity, or a combination of both factors. In recent years, herbal drugs and isolated plant bio actives have gained considerable interest because of their ability to produce blood glucose-lowering, insulin-sensitising, antioxidative, anti-inflammatory and hypolipidemic actions via diverse cellular signalling mechanisms. However, therapeutic application of several potent antidiabetic phytomolecules remains challenging as they possess less than 10% oral bioavailability, attributed to poor lipid solubility, low intestinal permeation, instability in the gastric environment, high hepatic first-pass metabolism and active efflux by P-glycoprotein transporters. The phytosome approach, also described as Phyto-phospholipid complexation, offers a viable strategy to address these biopharmaceutical constraints. In this technology, standardised herbal extracts or purified phytoconstituents are bound at the molecular level with phospholipids, mainly phosphatidylcholine, through formation of hydrogen bonds. In contrast to traditional liposomes where the drug is physically entrapped, phytosomes involve chemical interaction between polar functionalities of the phytoconstituent and the polar head region of phospholipid. Such molecular association improves amphiphilic nature, dispersion behaviour, affinity towards biological membranes, stability in the gastrointestinal tract, intestinal uptake and systemic availability of poorly absorbed herbal compounds. Consequently, phytosomes display superior pharmacokinetic and pharmacodynamic performance when compared to conventional extracts. The current review highlights fundamental principles, components, methods of preparation, evaluation parameters and underlying mechanisms responsible for bioavailability enhancement by the phytosome system, with special emphasis on antidiabetic phytoconstituents belonging to flavonoid, alkaloid, polyphenol, terpenoid and saponin categories.