Diosmin is a naturally occurring flavonoid glycoside that can be isolated from various plant sources or derived from the flavonoid hesperidin. Diosmin was first isolated in 1925 from Scrophularia nodosa, and first introduced as a therapeutic agent in 1969. Diosmin is considered to be a vascular-protecting agent used to treat chronic venous insufficiency, hemorrhoids, lymphedema, and varicose veins. As a flavonoid, diosmin also exhibits anti-inflammatory, free-radical scavenging, and antimutagenic properties. Diosmin differs molecularly from hesperidin by the presence of a double bond between two carbon atoms in diosmin’s central carbon ring. Diosmin can be manufactured by extracting hesperidin from citrus rinds, followed by conversion of hesperidin to diosmin. Diosmin has been used for more than 30 years as a phlebotonic and vascular-protecting agent, and has recently begun to be investigated for other therapeutic purposes, including cancer, premenstrual syndrome, colitis, and diabetes.