Formulation of Phytosomes Containing Rubia cordifolia Extract for Neuropathic Pain: In Vitro and In Vivo Evaluation

This study aimed to develop a delivery system for the dried aqueous extract of Rubia cordifolia leaves (RCE) that could improve the neuroprotective potential of RCE by improving the bioavailability of the chief chemical constituent rubiadin. Rubiadin, an anthraquinone chemically, is a biomarker phytoconstituent of RCE. Rubiadin is reported to have strong antioxidant and neuroprotective activity but demonstrates poor bioavailability. In order to resolve the problem related to bioavailability, RCE and phospholipids were reacted in disparate ratios of 1:1, 1:2, and 1:3 to prepare phytosome formulations PC1, PC2, and PC3, respectively. The formulation PC2 showed particle size of 289.1 ± 0.21 nm, ζ potential of -6.92 ± 0.10 mV, entrapment efficiency of 72.12%, and in vitro release of rubiadin of 89.42% at pH 7.4 for a period up to 48 h. The oral bioavailability and neuroprotective potential of PC2 and RCE were assessed to evaluate the benefit of PC2 formulation over the crude extract RCE. Formulation PC2 showed a relative bioavailability of 134.14% with a higher neuroprotective potential and significantly (p < 0.05) augmented the nociceptive threshold against neuropathic pain induced by partial sciatic nerve ligation method. Antioxidant enzyme levels and histopathological studies of the sciatic nerves in various treatment groups significantly divulged that PC2 has enough potential to reverse the damaged nerves into a normal state. Finally, it was concluded that encapsulated RCE as a phytosome is a potential carrier system for enhancing the delivery of RCE for the efficient treatment of neuropathic pain.