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

Objective:To optimize the ultrasonication method for efficient extraction ofβ-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 extractβ-sitosterol and lupeol from Astragalus atropilosus(roots).RSM was used to optimize the different extraction parameters viz.liquid to solid ratio(10–14 m L/g),temperature(60-80℃)and time(40–60 min)to maximize the yield ofβ-sitosterol and lupeol.The quantitative estimation ofβ-sitosterol and lupeol was done in chloroform extract of Astragalus atropilosus by validated HPTLC method on 10 cm×20 cm glass-backed silica gel 60 F254 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=0.9948/0.28),R2(β-sitosterol yield;R2/%CV=0.9923/0.39)and R3(lupeol yield;R2/%CV=0.9942/0.97).The values of adjusted R2/predicted R2/signal to noise ratio for R1,R2,and R3 were 0.9782/0.9551/48.77,0.9904/0.9110/31.33,and 0.9927/0.9401/36.08,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 0.9905-0.9973.β-sitosterol and lupeol in chloroform extract of Astragalus atropilosus were detected at Rf values of 0.22 and 0.34,respectively,atλmax=518 nm.The optimized ultrasonic extraction produced 8.462%w/w of R1,0.451%w/w of R2 and 0.172%w/w of R3 at 13.5 m L/g liquid to solid ratio,78℃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 ofβ-sitosterol and lupeol in other species of Astragalus.