Quantitative Phytochemicals Determination of the Extracts from the Flowers of <i>Alstonia scholaris</i> and their Anti-Lipoxygenase Activities

Abstract

Alstonia scholaris (L.) R. Br. (Apocynaceae) is a plant with various pharmacological activities, especially anti-inflammatory activity. There were rare reports about the phytochemicals of its flowers. This study aimed to determine the chemical constituents of the extracts from A. scholaris flowers along with screening for their anti-lipoxygenase activities. The fresh flowers (40 kg) of A. scholaris were dried at 45 ◦C and powdered (4 kg, 10% yield of fresh flower). The powder of dry flowers (4 kg) were extracted with 95% ethanol by using ultrasonic assistance to obtain ethanolic crude extract (ASF-EtOH) 201 g (5% yield of dry flower). The ASF-EtOH (100 g) was further subjected to liquid-liquid partition to obtain dichloromethane layer (ASF-DCM), ethyl acetate layer (ASF-EtOAc) and water layer (ASF-Water) around 26.4 g (26.4% yield), 9.3 g (9.3% yield) and 46.6 g (46.6% yield), respectively. All of the extracts were quantified for their chemical compositions by using colorimetric methods. Then their anti-lipoxygenase activities were evaluated by using linoleic acid as a substrate and lipoxygenase as an enzyme. The results indicated that one gram of ASF-EtOH, ASF-DCM, ASF-EtOAc and ASF-Water contained total alkaloids, cardiac glycosides, flavonoids and triterpenoids in the range of 1.25-5.15 mg berberine chloride equivalent, 4.47-36.64 mg digoxin equivalent, 37.87-40.16 mg rutin equivalent and 110.88-359.32 mg ursolic acid equivalent, respectively. The inhibitory effects towards lipoxygenase enzyme of ASF-EtOH, ASF-DCM, ASF-EtOAc (0.2 mg/ml) were 73.7, 89.9 and 67.4 %, respectively, which were higher than that of diclofenac sodium, an anti-inflammatory drug, at the same concentration. While ASF-Water (1 mg/ml) inhibited lipoxygenase activity around 19.4%. These results exhibited potential of the flowers of A. scholaris to provide plenty of secondary metabolites with potent anti-lipoxygenase activity. Therefore, the flowers of A. scholaris is a good material for further purification and discovery of anti-lipoxygenase agent.