OBJECTIVE: To find scientific reasons for adverse events reported in Traditional Iranian Medicine (TIM) following administration of aqueous extract of Herba Portulacae Oleraceae seed including itching and tingling of whole body, tachycardia, anxiety, dyspnea and severe nausea. METHODS: Electronic databases including PubMed, Scopus, and Web of Science were searched up to April 2013 to find papers focused on phytochemistry and biological activities of this plant. RESULTS: Among chemical constituents present in Herba Portulacae oleraceae, catecholamines, adenosine and niacin can cause adverse events similar to those reported inTIM. CONCLUSION: Because of the short duration of action of adenosine, catecholamines and niacin seems to be the major role in appearance of ad-verse events reported in TIM for Herba Portulacae Oleraceae seed. Mechanisms with consideration of receptor types and pharmacokinetics of catecholamine and niacin are warranted to confirm this hypothesis.