Cancer chemoprotective compositions containing reduced oil-content extraction meals made from plants containing natural oils and glucosinolates. The oil content of the extraction meals may be reduced using batchwise or continuous supercritical fluid extractions. Also provided are glucosinolate-rich compositions containing purified glucosinolates isolated from plant materials. The glucosinolate-rich compositions may be made by reducing the oil content of a plant materials containing natural oils and glucosinolates and isolating the glucosinolates from the reduced oil-content plant materials using a membrane extraction. Natural oils containing isothiocyanates are also provided. The natural oils are well-suited for use in skin and hair care products.