Identification of Five Phytosterols from Aloe Vera Gel as Anti-diabetic Compounds

Abstract

Of the more than 360 Aloe species known, Aloe barbadensis MILLER (Aloe vera) is the most widely used. Aloe vera contain two major parts: firstly, leaves containing a high concentration of anthraquinone compounds that have been used throughout the centuries as a cathartic and for medicinal purges; and secondly, a clear gel that has been used as a food and to treat burns and other wounds. 1,2) Several chemical components of the Aloe gel are thought to be responsible for its wound healing and immunostimulatory properties. For example, glycoprotein Aloectin A is reported to have anti-tumor and anti-ulcer effects, 3) and a 29 kDa glycoprotein has been found to increase proliferation of normal human dermal cells. 4) Most of these polysaccharides are glucomannans, mannans, or pectins with a range of molecular weights. A major focus of research has been on the carbohydrate fraction isolated from Aloe gel known as "acemannan," which comprises a polydispersed b-(1,4)-linked acetylated mannan interspersed with O-acetyl groups. 5)As a result of these studies, there have been numerous reports of Aloe having diverse biological activities, including anti-tumor activity, anti-acid activity, 6) tyrosinase inhibiting activity, 7) and antioxidant activity. 8)Two clinical trials are available from the same research group that reported hyperglycemic effects on fasting blood glucose as well as on HbA1c levels 9,10) with Aloe vera gel. Hikino et al. isolated two hyperglycemic polysaccharides from Aloe arborescens at 1985. 11) Beppu et al. separated two different anti-diabetic components from the leaf pulp and leaf skin of the same plant. A previous study made with Kidachi Aloe (Aloe arborescens var. naralensis) in streptozotocin (STZ)-induced diabetic rats confirmed its efficacy through administration, 12) contrary to Koo who reported hyperglycemic effects in diabetic rats in acute phase with a product containing Aloe vera gel. 13)In this study, we sought to determine the constituents of Aloe vera gel extract that normalize hyperglycemia in the diabetic mouse strain BKS.Cg-m ϩ/ϩ Lepr db/J (db/db), which exhibits many of the metabolic disturbances of human type 2 diabetes including hyperglycemia, obesity, and insulin resistance. Hemoglobin A1c (HbA1c), a binding product of glucose and hemoglobin, increases depending on the severity of hyperglycemia in a glucose level-dependent manner, and the level of HbA1c reflects the past blood glucose control conditions over a long period. Therefore, we tried to isolate the bioactive compounds from Aloe vera gel based on their ability to decrease the HbA1c level of db/db mice. Finally, we examined whether phytosterols and fractions isolated from Aloe vera gel play an important role in anti-hyperglycemic activity. MATERIALS AND METHODS General ProcedureMelting points were determined on a micro melting point apparatus (Yanako MP-3) without correction. NMR spectra were recorded using a Varian Unity-500 spectrometer ( C: 125 MHz). Positive APCI-MS was taken with LC-MS 2000 (Shimadzu).Preparation of Ext...

Hypoglycemic and hypolipidemic effect of Aloe vera L. in non-insulin dependent diabetics

“…Similar to findings of the present study, a significant reduction in blood glucose level was observed after administration of phytosterols such as lophenol, 24-methyl-lophenol, 24-ethyl-lophenol, cycloartanol and 24-methylene-cycloartanol in non insulin dependent diabetes by Tanaka et al (2006). Arora et al (2009) also reported a significant reduction in total cholesterol, total triglycerides, LDL, and VLDL levels after supplementation of Aloe vera.…”

Chemical composition and evaluation of possible alpha glucosidase inhibitory activity of eight Aloe species

“…1= Glucuronic acid; 2=Stachyose; 3= Galacturonic acid;4=Sucrose; 5=Maltose;6=Lactose ; 7=D-glucose ;8=Glucose; 9=Xylose; 10=Galactose; 11= Rhamnose; 12=Mannose; 13=Raffinose ;14=Arabinose;15=Fructose; ;16=Mannitol;17=Sorbitol;18=ribose. compounds, which can counter the high cost and poor availability of the current medicines for many rural populations in developing counties (Tanak et al, 2006).…”

Role of Glucomannans in Immunology

“…Jia et al (82) reported that topical applications of Aloe vera mucilage led to enhanced healing of wounds in both desert rats and rabbits. In general, Aloe vera contains a range of phytochemicals such as pyrocatechol, saponin, acemannan, β-mannan, anthraquinone, Cglycosides, diethylhexylphth-alate, bradykininase, oleic acid, phytol, and magnesium lactate along with water-soluble polysaccharides like glucomannan (75,(83)(84)(85). In addition to these components, vitamins (vitamin E and C) and amino acids do exist and may well play important role in acceleration of wound healing (77,86).…”