Optimization of infrared-assisted extraction of bioactive lactones from Saussurea lappa L. and their effects against gestational diabetes

Abstract

Background: Saussurea lappa (S. lappa, Asteraceae) have immunomodulatory effects and used in the management of many metabolic disorders. Gestational diabetes is one of the metabolic disorders affecting globally one in seven pregnant women. Objectives: The aim of the current study is to optimize an infrared-assisted extraction (IR-AE) method for S. lappa bioactive constituents, phytochemically investigate its content, isolate its most active constituent, and to assess their biological effects against gestational diabetes. Materials and Methods: To optimize IR-AE conditions, four main factors were studied including solvent concentration, extraction time, powder size, and IR power in the yielded extract (SL-IR). Reversed-phase high-performance liquid chromatography coupled with bio-guided fractionation and isolation procedures using 1H and 13C NMR method were utilized. Solid–liquid (SL-SLE) and ultrasound (SL-US) extraction methods were also done. Results: The optimal IR-AE extraction conditions were found to be 20% aqueous phase concentration, 60-min extraction time, 70 mesh powder size, and 70 W IR power. Phytochemically, four major lactones were identified, including costunolide, dehydrocostuslactone, isoalantolactone, and alantolactone (ATL). ATL was the most active lactone. SL-IR, SL-US, SL-SLE, or ATL showed a significant (P Abbreviations used: IR-AE: Infrared-assisted extraction; SL: Saussurea lappa, S. lappa; SL-IR: Saussurea lappa infrared extract; SL-US: Saussurea lappa ultrasound extract; SL-SLE: Saussurea lappa solid–liquid extract; ATL: Alantolactone; NDC: Nondiabetic control; DC: Diabetic control; MTF: Metformin; TBARS: Thiobarbituric acid; GSH: Reduced glutathione; CAT: Catalase; APA: Adequate for pregnancy age; LPA: Large for pregnancy age; SPA: Small for pregnancy age.