Phytochemical content and anti-inflammatory activity of chitosan nanoparticles loaded with <i>Annona muricata</i> L. (Annonaceae) stembark extract in Wistar rats

Abstract

The stembark of Annona muricata L. has been used by some communities in Nigeria for the treatment of pain, inflammation, cancer, fevers and other diseases for many decades. This present study was carried out to evaluate the phytochemical contents as well as the anti-inflammatory activity of A. muricata methanol stembark extract in carrageenan and formalin-induced Wistar rat models. The preliminary phytochemical screening of A. muricata methanol stembark extract (AMSE) was determined following standard methods while the acute oral toxicity test of AMSE was determined in five Wistar rats of opposite sex using the OECD guideline 425. The anti-inflammatory activity of the extract was evaluated using carrageenan-induced rat paw oedema. The results of the phytochemical screening showed the presence of flavonoids, alkaloids, tannins, saponins, and cardiac glycosides. GC-MS analysis of methanol stembark extract showed the presence of many compounds including phytol, oleic acid, oleyl alcohol, 2-pentadecanol, n-hexadecanoic acid, etc. Oral acute toxicity of AMSE showed that extract was well tolerated by the animals at the dose of 5000 mg/kg body weight after one week. Neither signs of toxicity nor mortality were witnessed in the animals, especially within the first 24 hours of oral toxicity testing. The anti-inflammatory evaluation of stembark extract at the doses of 300, 600 and 1200 mg/kg body weight (i.p.) showed a dose-dependent decrease in rat’s paw oedema in both carrageenan-induced rat paw oedema. These decreases were significant (p < 0.05) when compared to that of the standard drug (Diclofenac sodium 10 mg/kg; i.p.). The results from the study showed that chitosan NPs loaded with A. muricata methanol stembark extract possessed more anti-inflammatory activity than the crude extract by suppressing the production of pro-inflammation mediators. The study justifies the acclaimed use of A. muricata stembark extract in traditional medicine for the treatment of inflammation.