In the present study, the role of the phenolic compounds and the pollen grains as differential diagnosis of Senna senna plants grow in the valleys and on the mountains of Makkah was demonstrated. Since Senna is a member of the anthracene group of purgatives, its active principle being derivatives of anthraquinone. The present work aimed also at investigating its phenolic compounds that have medicinal significance. Flavonoids were classified according to their chemical structure to three groups: O-Flavonols were represented by apigenin. It was accompanied by its C-Flavone and vitexin. Both hydrolysable and condensed tannins were detected. Three phenolic acids were detected; 3-4-dihydroxybenzoic acid, 2,3-dihydroxybenzoic acid, and 2,5-dihydroxybenzoic acid. Phloroglucinol, [-]-epicatechin; the precursor of condensed tannins and [+]-catechin, the flavan desivative were also detected. The medicinal importance of the isolated phenolic compounds was given. Generally, the pollen grain of the studied taxa of the genus Senna  growing in the valleys and the mountains of Makkah are radically symmetrical, isopolar, tricolporat, and triangular trilobed with fossulate sculpture. The chemotaxonomical and palynological studies of the studied taxa of the genus Senna growing in the valleys and the mountains of Makkah are radically symmetrical, isopolar, tricolporat, and triangular trilobed with fossulate sculpture. The chemotaxonomical and palynological studies of the studied taxa of the genus Senna are not inagreement except for the flowers. Therefore, further details of the flavonoid constituents and their distribution especially of those which are less widespread, are to be studied because as understanding of their chemical properties will be helpful in the interpretation of their chemotaxonomical properties of Senna senna plants.