Enrichment of the major bioavailable molecule glucuronated flavone TMMG in Spinacia oleracea ameliorates cartilage degeneration at a lower dose in ACLT-induced osteoarthritis†

Abstract

Spinacia oleracea extract (SOE) showed a protective effect on cartilage against osteoarthritis, with one of its compounds, 5,3′,4′-trihydroxy-3-methoxy-6,7-methylenedioxy-flavone4′-glucuronide (TMMG), identified as a major bioavailable molecule with chondroprotective properties. Our recent study aimed to assess the potential of Spinacia oleracea enriched extract (SOEE) containing TMMG in alleviating osteoarthritis symptoms, facilitating easier determination of the human equivalent dose. Using an animal model simulating post-traumatic osteoarthritis, rats underwent anterior cruciate ligament transection (ACLT), with untreated animals serving as controls. Four weeks post-surgery, ACLT rats were randomly assigned for treatment with SOEE orally administered at doses of 10 and 20 mg kg⁻¹ d⁻¹ for four weeks. A positive control group was administered with crude SOE (125 mg kg⁻¹ d⁻¹; ∼1% TMMG). Two days prior to the termination of the animal study, behavioural analysis was done through open field activity and rotarod tests to assess the locomotive activity. Furthermore, data analysis was done through HPLC (high-performance liquid chromatography). Additional investigations corroborated chondroprotective effects via gross morphology of the knee joint, histological assessment of tibial articular cartilage, serum biochemical analysis of cartilage degradation markers, and micro-CT (micro-computed tomography). In conclusion, SOEE at 10 mg kg⁻¹ d⁻¹ demonstrated superior chondroprotective efficacy when compared to its 20 mg kg⁻¹ d⁻¹ dosage as well as SOE alone. Further investigation could lead to establishing a human equivalent dose of 1.522 mg kg⁻¹ for osteoarthritis treatment.