Comparative assessment of flavonoid content in banana pulp and peel and their role in mitigating bone loss conditions and promoting osteoblast differentiation†

Banana fruit is widely grown and serves as a source of income across the tropics. It is known for its nutritional qualities and well-recognized medicinal applications. Given that banana pulp and peel are rich in flavonoids, such as naringenin, kaempferol, and quercetin, which are already known for their role in bone health, we hypothesize that banana pulp and peel can accelerate fracture healing, mitigate bone loss in post-menopausal conditions, and promote osteoblast differentiation. The current study was proposed to assess a comparative and parallel investigation of the differential flavonoid expression in banana pulp and peel and their concomitant bone anabolic effects. The pulp extract exhibited its osteogenic potential when administered orally for 2 weeks at doses of 250, 500 and 750 mg per kg per day in the osteotomy Balb/c mice model (n = 10), while the peel extract showed similar effects at comparatively much lower doses of 50, 100 and 250 mg per kg per day for the same duration. The effective lower doses in both cases, i.e., 250 mg per kg per day for the pulp and 50 mg per kg per day for the peel, were used to further investigate the anti-osteoporotic potential in vivo over a span of 8 weeks (n = 10). Banana pulp ameliorated the microarchitectural deterioration of the bones by increasing the rate of bone formation while simultaneously limiting exaggerated resorption, as assessed by micro-CT, calcein labelling, TRAP staining, bone strength parameters and measurement of bone formation and resorption markers in serum. Similar results were obtained with the banana peel extract at considerably lower doses. The osteogenic potential of the pulp and peel extracts was also tested in an in vitro setup. Osteoblast viability and differentiation, as assessed by MTT, ALP, mineralization and RT-PCR, demonstrated that bone formation potential was observed at 2.5 μg ml⁻¹ and 5 μg ml⁻¹ of the pulp extract, whereas in the case of the peel extract, it was observed at 0.625 μg ml⁻¹ and 1.25 μg ml⁻¹. These findings indicate that banana peel can exert similar osteogenic and osteoprotective effects as the pulp but at a much lower dose. This highlights banana peel as a prospective, sustainable feedstock for the healthcare sector, providing an alternative to its disposal.