title: Biocatalytic conversion of aloeresin A to aloesin.
abstract: Leaf exudates from Aloe species, such as the Southern African Aloe ferox, are used in traditional medicines for both humans and livestock. This includes aloesin, a skin bleaching product that inhibits the synthesis of melanin. Aloesin, (a C-glycoside-5-methylchromone) can be released from aloeresin A, an ester of aloesin, through hydrolysis. The objective of the current study was to identify an enzymatic hydrolysis method for converting aloeresin A to aloesin, resulting in increased concentrations of aloesin in the aloe bitters extract. More than 70 commercially available hydrolytic enzymes were screened for the conversion of aloeresin A. An esterase (ESL001-02) from Diversa, a lipase (Novozym 388) and a protease (Aspergillus oryzae) preparation were identified during screening as being capable of providing conversion of pure aloeresin A, with the protease giving the best conversion (~100%). It was found that a contaminating enzyme in Novo 388 was responsible for the conversion of aloeresin A to aloesin. This contaminating enzyme, possibly a protease, was able to give almost complete conversion using crude aloe bitters extract, doubling the concentration of aloesin in aloe bitters extract via the hydrolysis of aloeresin A.
authors.affiliation: Protein Technologies, CSIR Biosciences, P.O. Box 395, Pretoria, 0001, South Africa. lsteenkamp@csir.co.za
authors.forename: Lucia
authors.initials: L
authors.lastname: Steenkamp
authors.forename: Kgama
authors.initials: K
authors.lastname: Mathiba
authors.forename: Paul
authors.initials: P
authors.lastname: Steenkamp
authors.forename: Vuyisile
authors.initials: V
authors.lastname: Phehane
authors.forename: Robin
authors.initials: R
authors.lastname: Mitra
authors.forename: Steven
authors.initials: S
authors.lastname: Heggie
authors.forename: Dean
authors.initials: D
authors.lastname: Brady
mesh_terms: D000353:Africa, Southern; D000504:Aloe / Q000737:chemistry* / Q000201:enzymology; D001236:Aspergillus oryzae / Q000201:enzymology; D055162:Biocatalysis; D002867:Chromones / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D004950:Esterases / Q000378:metabolism; D005960:Glucosides / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D006868:Hydrolysis; D008049:Lipase / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism; D010936:Plant Extracts / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry / Q000201:enzymology; D062327:Skin Lightening Preparations / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D002867:Chromones; D005960:Glucosides; D010936:Plant Extracts; D062327:Skin Lightening Preparations; C521199:aloeresin A; D004950:Esterases; D008049:Lipase; D010447:Peptide Hydrolases; C069868:aloesin