The samples (leaves) were collected from Calotropis procera found at their natural habitat of Khanpur Valley in the sub Himalayan Mountains of Pakistan and chemical analysis was carried out at the University of Agriculture Peshawar. Significant effects were observed at different seasons and sites upon various bio-chemical substances. Calotropis procera revealed higher significant values for crude proteins (14.58%) at Mang during summer, crude fibers (13.39%) at Dabola during winter, crude fats (11.98%) at Jabri during summer, NFES (50.80%) at Dam during winter, NFEE (203.1%) at Jabri during summer, potassium (500.33mg/100g) at Dam during summer, calcium (274.07mg/100g) at Dabola during winter, magnesium (291.57mg/100g) at Dabola during winter, copper (0.72mg/100g) at Jabri during summer, iron (291.6mg/100g) at Dam during summer manganese (19.27mg/100g) at Dam during summer and zinc (6.03mg/100g) at Mang during winter. It was concluded from the results of the current experiment that medicinal plants under study were rich in bio-chemical substances. Calotropis procera showed maximum bio-chemicals in the samples collected during last week of July.

KEY WORDS: Bio-chemical substances, Khanpur Valley, Natural habitat, Summer, winter.