Physicochemical Characterization and Biological Activities of the Triterpenic Mixture α,β-Amyrenone

Abstract

α-Amyrenone and β-amyrenone are triterpenoid isomers that occur naturally in very low concentrations in several oleoresins from Brazilian Amazon species of Protium (Burseraceae). This mixture can also be synthesized by oxidation of α,β-amyrins, obtained as major compounds from the same oleoresins. Using a very simple, high yield procedure, and using a readily commercially available mixture of α,β-amyrins as substrate, the binary compound α,β-amyrenone was synthesized and submitted to physico-chemical characterization using different techniques such as high-performance liquid chromatography, nuclear magnetic resonance (¹H and ¹³C), mass spectrometry, scanning electron microscopy, differential scanning calorimetry, thermogravimetry and derivative thermogravimetry, and Fourier transform infrared spectroscopy (FTIR). Biological effects were also evaluated by studying the inhibition of enzymes involved in the carbohydrate and lipid absorption process, such as α-amylase, α-glucosidase, lipase, and their inhibitory concentration values of 50% of activity (IC₅₀) were also determined. α,β-Amyrenone significantly inhibited α-glucosidase (96.5% ± 0.52%) at a concentration of 1.6 g/mL. α,β-Amyrenone, at a concentration of 100 µg/mL, showed an inhibition rate on lipase with an IC₅₀ value of 82.99% ± 1.51%. The substances have thus shown in vitro inhibitory effects on the enzymes lipase, α-glucosidase, and α-amylase. These findings demonstrate the potential of α,β-amyrenone for the development of drugs in the treatment of chronic metabolic diseases.

Keywords: Protium; amyrenone; amyrin; enzymatic activity; triterpenes.

Figure 1

The synthesis of oxidized derivatives of a mixture of α-amyrin (R₁ = H, R₂ = CH₃) and β-amyrin (R₁ = CH₃, R₂ = H). (a) Pyridinium-chlorochromate (CCP), CH₂Cl₂.

Figure 2

HPLC: (A) peak hold of α,β-amyrenone mixture; (B) Peak purity index of 0.996605 of α and β-amyrenone.

Figure 3

X-ray diffraction pattern of α,β-amyrenone (A); and surface morphological appearance of α,β-amyrenone (B).

Figure 4

Differential thermal analysis (DTA), differential scanning calorimetry (DSC) and thermogravimetry (TG)/derivative thermogravimetry (DTG) curves for α,β-amyrenone in heating rate of 10.0 °C·min⁻¹.

Figure 5

(A) Inhibitory Activity (%) of isomers of α,β-amyrenone on α-glucosidase enzyme. The data analyzed in t test demonstrated value of 0.0002; (B) Inhibitory Activity (%) of α,β-amyrenone on pancreatic lipase enzyme and comparison with the standard orlistat.