Background: In some developing countries and due to economic conditions, plant seeds are used as a medicinal source to treat infectious diseases.  The seeds are the main medicinal part of the plant.  Phenolic compounds are secondary metabolites that have diverse structures containing one or more hydroxyl groups produced by plants mainly for protection against biotic or abiotic stress.  A study of its exposure is essential in order to obtain a higher yield of these valuable compounds.  The aim of this research is to study the influence of UVA on molecular structure, chemical composition and photochemistry compounds of Salvia hispanica.  Materials and methods: Salvia hispanica seeds were received from the Egyptian Ministry of Agriculture.  The total phenolic content was determined using the Florin-Ciocalteu method.  The total flavonoids content was determined using the aluminum chloride method.  Results: UVA caused a great effect on molecule arrangement, size and orientation, chemical composition, enzymatic and non-enzymatic antioxidants in Salvia hispanica.  Total phenolic content in Salvia hispanica varied after exposure to UVA for 1, 2, 3 and 4 hours at 5 cm and 20 cm from UV source.  Total flavonoids content in Salvia hispanica varied after exposure to UVA.  Also, DPPH scavenging activity, phenolic and flavonoids in Salvia hispanica varied after exposure to UVA.  A significant change in carbohydrates, protein and fats with little variation in total fibers in Salvia hispanica after exposure to UVA.