Response surface methodology-based optimization of ultrasound-assisted extraction of β-sitosterol and lupeol from astragalus atropilosus (roots) and validation by HPTLC method

Abstract

Objective: To optimize the ultrasonication method for efficient extraction of P-sitosterol and lupeol from the roots of Astragalus atropilosus using Box-Behnken design of response surface methodology (RSM), and its validation by high performance thin layer chromatography (HPTLC) method. Methods: Ultrasonication method was used to extract β-sitosterol and lupeol from Astragalus atropilosus (roots). RSM was used to optimize the different extraction parameters viz. liquid to solid ratio (10-14 mL/g), temperature (60-80 °C) and time (40-60 min) to maximize the yield of β-sitosterol and lupeol. The quantitative estimation of β-sitosterol and lupeol was done in chloroform extract of Astragalus atropilosus by validated HPTLC method on 10 cm × 20 cm glass-backed silica gel 60F254 plate using hexane and ethyl acetate (8:2, v/v) as mobile phase. Results: A quadratic polynomial model was found to be most appropriate with regard to R1 (yield of total extraction; R2/% CV = 0.994 8/0.28), R2 (β-sitosterol yield; R2/% CV = 0.992 3/0.39) and R3 (lupeol yield; R2/% CV = 0.994 2/0.97). The values of adjusted R2/predicted R2/signal to noise ratio for R1, R2, and R 3 were 0.978 2/0.955 1/48.77, 0.990 4/0.911 0/31.33, and 0.992 7/0.940 1/36.08, respectively, indicating a high degree of correlation and adequate signal. The linear correlation plot between the predicted and experimental values for R1, R2, and R3 showed high values of R2 ranging from 0.990 5-0.997 3. β-sitosterol and lupeol in chloroform extract of Astragalus atropilosus were detected at Rf values of 0.22 and 0.34, respectively, at X max = 518 nm. The optimized ultrasonic extraction produced 8.462% w/w of Rl, 0.451% w/w of R2 and 0.172% w/w of R3 at 13.5 mL/g liquid to solid ratio, 78 C of temperature and 60 min of time. Conclusions: The experimental findings of RSM optimized extraction and HPTLC analysis can be further applied for the efficient extraction of β-sitosterol and lupeol in other species of Astragalus.

Keywords

• β-sitosterol; lupeol; box-behnken design; astragalus; high performance thin layer chromatography