The present invention relates to a pharmaceutical composition having dopaminergic activity and other related pharmaceutical activities comprising trigonelline or its derivative(s) and 4-hydroxyisoleucine or its derivative(s), optionally along with excipients(s); a process of preparing a pharmaceutical composition comprising trigonelline or its derivative(s) and 4-hydroxyisoleucine or its derivative(s), optionally along with excipients(s), wherein the process comprising steps of: (a) extracting a clear solution containing trigonelline and 4-hydroxyisoleucine from plant source; and (b) optionally precipitating derivative(s) of trigonelline and 4-hydroxyisoleucine from the clear solution and obtaining said composition; and an in-vitro method to increase levels of dopamine or to inhibit prolactin by allowing composition comprising trigonelline or its derivative(s) and 4-hydroxyisoleucine or its derivative(s) to bind to cell receptors.