Solvent free microwave assisted extraction of corosolic acid from banaba (Lagerstroemia speciosa) crude extract

Lagerstroemia speciosa crude extract was obtained through solvent-free microwave assisted extraction specifically concerning on the corosolic acid extraction from the plant fresh leaves, one-week air dried leaves and naturally dried fruits. Corosolic acid is reported to be responsible for anti-diabetic activity and is one of the important and highly studied contents of Lagerstromeia speciosa. This study showed that solvent free microwave assisted extraction is an effective tool in obtaining corosolic acid as its presence in the crude extract is indicated using the high performance liquid chromatography (HPLC). Conditions such as drying time, extraction time, microwave power and temperature were varied resulting to the best extraction. Fresh leaves show the greatest yield at 170 ºC at a power of 600W at extraction time of 1 hour since it has the greatest amount of moisture and water allows more rapid temperature increase in the sample heightening the recovery of the product from the extraction. For the corosolic acid content, the best condition is with fruit at 400 W and 85 ºC surpassing all the best conditions of fresh and dried leaves indicating that the fruits are a very good source of corosolic acid considering it is the least explored and tested for corosolic acid content from Lagerstroemia speciosa. The trend of results for leaves showed that at longer time of extraction, yield increases with temperature and power. Corosolic acid content is best extracted at a high power of 600W with extraction time of 1 hour and greatest at 150 ºC. It is the other way around for fruits which obtained lesser yields an amount of corosolic acid at higher temperature and power resulting to a best extraction condition of 85 ºC at 400W. This extraction method has save 99% of the time consumed by traditional solvent extraction for 72 hours