Barbaloin content of aloe (Aloe barbadensis) leaf exudates as affected by different drying techniques

Abstract

Aloe (Aloe barbadensis Mill.) is commercially cultivated for its transparent leaf gel and leaf exudates. The leaf exudates collected from epidermal layer contain anthraquinone glycosides (aloins) mainly barbaloin (aloin A) and isobarbaloin (aloin B). Aloin A is used as a raw material for the production of diacylrhein, a potent drug prescribed for rheumatoid arthritis. Conventional drying of leaf exudates in open sun causes changes in physicochemical properties and altered aloin A and B composition. Various drying techniques, viz. oven drying, freeze drying, shade drying and open sun drying were employed to evaluate the qualitative and physico-chemical changes in final product of aloe leaf exudates. Freeze drying resulted in high quality dried exudates having maximum aloin A content of 54.16%. The other three drying techniques resulted in lower aloin A content in the final dried product of leaf exudates. Fresh aloe exudates contained lower amount of aloin B (4.65% w/v). Sun drying increased aloin B content to 17.73% (to the extent of 2.27 fold) in the final product compared to freeze drying. Shade drying and sun drying lowered the total aloin content by 13.2% and 8% respectively compared to freeze dried exudates. Freeze drying is the most efficient technique to obtain high quality dried aloe exudates having good textural and physicochemical property. Alternately, shade drying with proper ventilation can be employed to get acceptable final product with marginally lower (8%) total aloin content compared to freeze drying.