HONG KONG, Jul 19 (Reuters) - Sihuan Pharmaceutical Holdings Group Ltd said it would sell a 50 percent stake in a wholly owned pharmaceutical products distributor to Shandong Buchang Pharmaceutical Co Ltd for 637.5 million yuan ($98.55 million). China's largest cardio-cerebral vascular (CCV) drugmaker said on Tuesday it would cooperate with Shandong Buchang to broaden its product portfolio to include traditional Chinese medicines for chronic treatment of CCV diseases. Shandong Buchang, a CCV drug and traditional Chinese medicine researcher and producer, has established an extensive network for sales and distribution of pharmaceutical products in China, Sihuan said. Shares of Sihuan fell 2.46 percent at midday on Tuesday versus a 0.29 percent fall in the Hang Seng Index.