Chromatographic fractionation of the alcoholic extract of leaves of Chorisia speciosa A. St. Hil. (Bombacaceae) resulted in the isolation and identification of ten compounds, two of them are firstly reported in the family: β-amyrin (1), and Verbascoside (7), in addition to five compounds firstly isolated from the plant p-hydroxy benzoic acid (3), β-sitosterol-3-O-β-d-glucopyranoside (4), succinic acid (5), astragalin (8) and cinaroside (9), in addition to β-sitosterol (2), tiliroside (6) and rhiofolin (10). Their structures were established by various spectroscopic methods (1H NMR, 13C NMR, HSQC, HMBC and UV spectroscopy) as well as comparison with authentic samples. Biological studies of different extracts of Chorisia speciosa A. St. Hil. showed that the extracts have slightly higher antioxidant activity.

Callistemon is an important genus in the family Myrtaceae which contains about 34 species. The members of this genus are known for their ornamental potentials, in addition to their outstanding value in conventional medicine in many parts of the world. Updated chemical analysis of the Callistemon genus has provided a variety of essential phytocompounds belonging to different chemical classes including terpenes, phenolic derivatives, flavonoids, anthocyanins, neolignans, phloroglucinol derivatives and other miscellaneous compounds. Hence, this dissertation reflects a systematic evaluation of the Callistemon genus phytochemical and biological studies, in addition to a summary of the previous studies’ results as well as an overview of the possible directions of Callistemon species study