The invention pertains to field of organic chemistry, medicine, pharmacology, foods and cosmetics industry, particularly, to manufacturing technology of selenoxanthenes; the invention may be used in manufacturing of food supplements, pharmaceutical and cosmetic products, having bioactive properties, of a wide spectrum of activity. The proposed compound is the .alpha.-crystalline form of 9-phenyl-symmetrical-octahydroselenoxanthene with exhibits antioxidant, detoxifying, immunomodulating, anti-atherogenic, anti-sclerotic, anabolic and hypolipidemic properties, and has the following structural formula: ##STR00001## Its powder X-ray diffractogram (obtained from a Cu-K X-ray source) has characteristic diffractions in degrees of the diffraction angle 2theta as 6.0, 12.0, 15.0, 17.0, 19.0, 20.0, 21.5, 21.7, 20.9, 25.0, 27.0, 28.0, 29.0, 37.0; the melting point of 96.8.degree. C. The crystalline form of the respective 9-R-symmetrical-selenoxantene product is obtained by crystallization from a weakly polar or a non-polar solvent.