This trial tests if fisetin, a natural substance from fruits and vegetables, can improve blood vessel health and reduce artery stiffness in older adults. It works by making old cells act younger, reducing cell stress, and lowering inflammation. The study will also check if fisetin is safe and well-tolerated. Fisetin is a natural flavonoid found in various fruits and vegetables, known for its antioxidant, anti-inflammatory, and anti-carcinogenic properties.