NOVELTY - A naphthoquinone compound CWL-168 (1,2,3,4-tetrahydro-1,2,5-trihydroxy-6,7-dimethoxy-3-methyl-9,10-)anthrone (I), is new.    USE - The naphthoquinone compound CWL-168 is useful for preparing medicine for treating cancer chosen from human gastric cancer, mouse melanoma, human breast cancer, human pancreatic cancer, human cervical carcinoma, bone cancer, human liver cancer, human colon cancer, and human laryngeal carcinoma (all claimed).    ADVANTAGE - The naphthoquinone compound CWL-168 is prepared in a simple, cost-effective and environmentally-friendly manner.    DETAILED DESCRIPTION - A naphthoquinone compound CWL-168 (1,2,3,4-tetrahydro-1,2,5-trihydroxy-6,7-dimethoxy-3-methyl-9,10-)anthrone of formula (I), is new. An INDEPENDENT CLAIM is included for method for preparing the above-mentioned naphthoquinone compound CWL-168, which involves (a) preparing bacterial culture by preparing seawater potato dextrose agar (PDA) medium comprising 200 g potato, 20 g glucose, 15-20 g agar and 1 l seawater, subjecting the medium to high temperature sterilization, placing the mixture at room temperature and inoculating Penicillium chrysogenum mycelium in the medium, (b) adding the seed culture medium in several Erlenmeyer flasks, subjecting the mixture to high-temperature sterilization, inoculating bacteria and preparing seed culture, (c) preparing fermentation medium (1 l) comprising 45 g small yellow rice, subjecting the mixture to high-temperature sterilization, and inoculating seed culture in the Erlenmeyer flasks, (d) aging the fermented mixture, adding 500 ml ethanol to the mixture, dissolving the fermented mixture in ethanol solution, collecting upper ethanol solution, again adding 500 ml ethanol to the mixture, extracting the mixture for three times, where each time the mixture is soaked in ethanol at room temperature for overnight to obtain primary extract, subjecting the extract to high-pressure emulsification dispersion and obtaining emulsified product, and (e) suspending the resulting extract in water, washing the suspended mixture using petroleum ether, extracting the mixture using ethyl acetate, concentrating the extract, purifying the extract by silica gel column chromatography, eluting the mixture using chloroform-methanol in a volume ratio of 98:5-10:90 as eluent, performing gradient elution by thin-layer chromatography using chloroform-acetone-acetic acid in a volume ratio of 30:10:1, purifying the obtained eluted mixture using Sephadex (RTM: Cross-linked dextran gel) LH-20 column using chloroform-acetone in a volume ratio 5:2, eluting the mixture, collecting 15 ml eluted mixture in 20 tubes, combining the eluted mixtures in 9-12 tubes and concentrating and drying the mixture.