A comparative study of different solvents and extraction techniques on the anti-oxidant and enzyme inhibitory activities of Adansonia digitata L. (Baobab) fruit pulp

Adansonia digitata L. (Malvaceae), also known as Baobab, is well known in Africa for its significant role in international trade and as important source of food, folk medicine and income to rural communities in Africa. The fruit pulp have been used in Sudan and many other countries as beverages and in traditional medicine for the treatment of malaria, fever and many gastrointestinal diseases. The objective of the study was to determine the best method for extraction of phenolic rich crude extracts from A. digitata fruit pulp with high anti-oxidant (phosphomolybdenum, antiradical, reducing power and ferrous chelating) activity and enzyme inhibition activity against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, α-glucosidase, and α-amylase. Water, ethanol and 50% ethanol extracts were prepared using maceration, decoction and microwave techniques. Fruit pulp of A. digitata showed significant (p <.05) variable phenolic contents, anti-oxidant and enzyme inhibition capacity among solvent type and method of extraction. Microwave technique showed the highest polyphenolic content (66.40 ± 0.32 mg GAE/g) extracted by 50% EtOH, flavonoids (42.15 ± 0.12 mg QE/g) and anthocyanidin contents (2.37 ± 0.06 mg GAE/g) obtained by water. The highest anti-oxidant activity in all the five assays used, was obtained from EtOH extract subjected to maceration. Moreover, microwave technique improved significantly the anti-oxidant activity of 50% EtOH extract. The highest AChE inhibition activity was observed in the three techniques used when using 50% EtOH as solvent while maceration and decoction were effective for EtOH solvent. The highest activity against BChE was performed by EtOH extract subjected to microwave extraction. Epicatechin or (+)-Catechin were the major compounds obtained in all extracts except for 50% EtOH extracts obtained by maceration and decoction which were dominated by the presence of prorocatechuic acid. It is argued that the solvent used and extraction method had an influence on anti-oxidant and enzyme inhibition activities of extracts. In conclusion, maceration and ethanol are recommended as the appropriate extraction method and solvent to obtain phytoconstituents with highest anti-oxidant activities from fruit pulp of Baobab for pharmaceutical and nutraceutical development.