Opuntia monacantha: Validation of the anti-inflammatory and anti-arthritic activity of its polyphenolic rich extract in silico and in vivo via assessment of pro- and anti-inflammatory cytokines

Opuntia monacantha belongs to the cactus family Cactaceae and is also known by cochineal prickly pear, Barbary fig or drooping prickly pear. It was traditionally used to treat pain and inflammation. O. monacantha cladodes showed pharmacological effects such as antioxidant potential owing to the presence of certain polysaccharides, flavonoids, and phenols. This research aimed to evaluate the anti-inflammatory as well as the anti-arthritic potential of ethanol extract of Opuntia monacantha (E-OM). In vivo edema in rat paw was triggered by carrageenan and used to evaluate anti-inflammatory activity, while induction of arthritis by Complete Freund's Adjuvant (CFA) rat model was done to measure anti-arthritic potential. In silico studies of the previously High performance liquid chromatography (HPLC) characterized metabolites of ethanol extract was performed by using Discovery Studio 4.5 (Accelrys Inc., San Diego, CA, USA) within active pocket of glutaminase 1 (GLS1) (PDB code: 3VP1; 2.30 Å). EOM, particularly at 750 mg/kg, caused a reduction in the paw edema significantly and decreased arthritic score by 80.58% compared to the diseased group. It revealed significant results when histopathology of ankle joint was examined at 28th day as it reduced inflammation by 18.06%, bone erosion by 15.50%, and pannus formation by 24.65% with respect to the diseased group. It restored the altered blood parameters by 7.56%, 18.47%, and 3.37% for hemoglobin (Hb), white blood count (WBC), and platelets, respectively. It also reduced rheumatoid factor RF by 13.70% with concomitant amelioration in catalase (CAT) and superoxide dismutase (SOD) levels by 19%, and 34.16%, respectively, in comparison to the diseased group. It notably decreased mRNA expression levels of COX-2, IL-6, TNF-α, IL-1, NF-κβ and augmented the levels of IL-4 and IL-10 in real time PCR with respect to the diseased group and piroxicam. HPLC analysis previously performed showed that phenolic acids and flavonoids are present in E-OM. Molecular docking studies displayed pronounced inhibitory potential of these compounds towards glutaminase 1 (GLS1), approaching and even exceeding piroxicam. Thus, Opuntia monacantha could be a promising agent to manage inflammation and arthritis and could be incorporated into pharmaceuticals.