Diosmin is a flavonoid, or flavone-like plant pigment. This chemical is used to make medicines to treat hemorrhoids and conditions relating to poor blood circulation. Diosmin is often taken in conjunction with hesperidin, a citrus fruit flavonoid, and is considered safe to use for up to 3 months at a time. It does cause some side effects, including digestive discomfort and headache. Drug companies often extract diosmin directly from plants to use in medicines.
Citrus fruits, especially lemons, are rich sources of diosmin, according to "Food Chemistry." Lemons produce a number of useful flavonoids, including diosmin, in both the mature fruit and the leaves. Buddha's finger, a type of citron, is also rich in diosmin. According to the "Journal of Agricultural and Food Chemistry," green Meyer lemons and Buddha's finger fruits contain the highest diosmin levels, especially when treated with hormones during the early growth stages.
Members of the Vicia, or vetch, genus also contain diosmin, including Asian and Caucasian vetch species. Vetches are native to North America, Europe, Africa and Asia, and are related to peas and lentils. According to the "Pharmaceutical Chemistry Journal," Caucasian vetch leaves contain 2 percent diosmetin glycosides – a source of diosmin – after air drying. Extracting diosmin from these leaves can be complicated, and requires the use of solvents such as alcohol and dimethyl sulfoxide.
Herb hyssop, also called Hyssopus officinalis and Hyssopus decumbens, is another source of diosmin. This plant is native to Southern Europe and the Middle East, and tends to concentrate its diosmine in the leaves and flower sepals. According to "Planta Medica," hyssop leaves contain 51 percent of the plant's diosmin, while the sepals contain 40.5 percent of this flavanoid. Trace amounts of diosmin may be found in the rest of the herb hyssop plant.