Boysenberries
Named after their originator, Rudolph Boysen, boysenberries are a successful meld of blackberry, loganberry, and raspberry. Relatively large, these glossy, reddish-purple berries erupt with a distinct juicy tartness, whether enjoyed during their rather brief fresh season, quick-frozen, or in jams, preserves, and syrups.
It's all in the family
Like the rest of their blackberry family, boysenberries are one of the most powerful disease-fighting foods available. Naturally stocked with Vitamin C and fiber, and with an antioxidant level almost double that of blueberries, they have been shown to help reduce the risks of certain cancers and help fight free radical damage in the body. Boysenberries also contain a uniquely high free ellagic acid ratio, which is thought to make it more readily available to the body. Ellagic acid is a phenolic compound with potent anti-carcinogen, anti-viral, and anti-bacterial properties.
Source:"Boysenberry Characteristics" Oregon Raspberry and Blackberry Commission

