Get the healthy benefits of grapefruit seed extract while boosting the immune system! NutriBiotic DefensePlus Tablets contain Citricidal (grapefruit seed extract), a natural quaternary compound synthesized from the seed and pulp of certified organically grown grapefruit. This unique formulation combines Citricidal, vitamin C, astragalus, and the extracts of echinacea, reishi, maitake, shiitake, ginger root and yarrow and has been shown to be highly effective worldwide as nutritional support.