Grapefruit Seed Extract-All Purpose Liquid Concentrate 128 oz. Bottle. Nutribiotic® Liquid Concentrate contains CITRICIDAL®. CITRICIDAL; is a natural quaternary compound synthesized from the seed and pulp of certified organically grown grapefruit. The manufacturing process converts grapefruit bioflavonoid (polyphenolics); into an extremely potent compound that has been proven highly effective in numerous applications. CITRICIDAL is used by healthcare professionals worldwide as nutritional support for individuals with certain health concerns.