Topical Microgel Formulation Containing Tectona Grandis Bark Extract and Evaluation to Treat Arthritis in an Animal Model

Abstract

This study aimed to develop and evaluate a topical microgel formulation containing Tectona grandis bark extract for its anti-arthritic and anti-inflammatory activities in rats. Twelve topical gel formulations were prepared using Carbopol 934 (F1-F6) and Carbopol 940 (F7-F12) as gelling agents. These formulations were rigorously evaluated for physicochemical parameters, including net content, physical appearance, viscosity, extrudability, pH, spreadability, and in vitro diffusion profile. Primary skin irritation tests were also conducted to ensure the safety of the product. Among the prepared formulations, F4, formulated with 1.5% Carbopol 934 and 2% Tectona grandis bark extract, demonstrated superior organoleptic characteristics and active ingredient release.

The anti-arthritic activity of F4 was assessed in Freund’s Complete Adjuvant (FCA)-induced arthritic rats. Key parameters such as body weight, paw volume, haematological profiles (haemoglobin, ESR, RBC, WBC), biochemical markers (SGPT, SGOT, total proteins, creatinine, uric acid, urea nitrogen), and histopathological examination of joint tissues were evaluated over 28 days. Topical application of formulation F4 significantly (p < 0.01) reduced paw volume, restored haematological and biochemical parameters towards normal levels, and showed comparable anti-arthritic effects to standard diclofenac topical gel. Furthermore, histopathological analysis confirmed a reduction in inflammation in the treated groups. The in vitro release kinetics of F4 followed zero-order kinetics, indicating a controlled release profile. The skin irritation tests confirmed the non-toxic and safe nature of the developed microgel.

These findings suggest that the topical microgel formulation containing Tectona grandis bark extract, particularly F4, possesses significant anti-arthritic and anti-inflammatory properties, potentially attributed to the presence of Betulin. This formulation presents a promising alternative for the topical management of arthritis and inflammatory disorders.