Extraction and microencapsulation of polyphenol-rich antioxidant from Clinacanthus nutans for controlled release formulation

Abstract

Clinacanthus nutans (Burm.f.) Lindau is a herbal medicine traditionally consumed in Malaysia. Since most of herbal active compounds are complex and may cause interferences in human body, a delivery system is needed to control the delivery of the active compounds. Thus, this study aims to develop controlled release formulated C. nutans polyphenolic-rich antioxidant extracts. Firstly, standardize C. nutans extracts were prepared by extracting the leaves and stem by different extraction methods and type of solvents. The extracts were characterized based on the content of polyphenol (TPC), total flavonoid (TFC), four composition of C-glycoside flavones (vitexin, isovitexin, orientin, isoorientin), total antioxidant capacity (TAC) and other chemical antioxidant compounds using gas chromatography–mass spectrometry. Then, C. nutans leaves extracts were encapsulated in carrier agent (κC/CMC) and spray dried to obtain extract in powder form. The feed flow rate, inlet drying temperature and coating agent concentration were studied and the physicochemical properties and release profile for uncoated and coated spray-dried C. nutans were characterized. The antioxidant capacity of spray-dried C. nutans was then predicted using artificial neural network (ANN) model. From the results, a standardized extraction was obtained from C. nutans leaves extract using decoction method with high extraction efficiency of polyphenolic compounds and antioxidant properties with TPC of 44.76 mg gallic acid equivalent (GAE)/g, TFC of 7.39 mg quercetin equivalent (QE)/g, TACDPPH : 16.29 mg trolox equivalent antioxidant capacity (TEAC)/g; TACFRAP : 29.58 mg TEAC/g of dried extracts. The C. nutans leaves extracts enriched with flavonoid glycosides : isoorientin (811.0 µg/mL) as major compound, followed by isovitexin (204.9 µg/mL), orientin (138.5 µg/mL) and vitexin (135.6 µg/mL). The C. nutans extracts was successfully encapsulated in κC/CMC by spray drying process at 700 mL/h of feed flow rate, 130 °C of inlet drying temperature and 0.5 % (w/v) coating agent concentration with high encapsulation yield (25.5 %) and high antioxidant capacities (TPC: 41.9 mg GAE/g, TFC: 11.6 mg QE/g, TACDPPH: 1.3 mg TEAC/g of spray-dried powders). ANN modeling was able provide satisfactory prediction for antioxidant capacities of spray-dried C. nutans with high correlation coefficient (R2) determination for TPC (R2: 0.8697), TFC (R2: 0.6562), vitexin (R2: 0.9543), isovitexin (R2: 0.9445), orientin (R2: 0.9586), isoorientin (R2: 0.8396), and total antioxidant activity (R2 = 0.8599). The spray-dried encapsulated C. nutans had smooth surface and spherical shape with small particle size range between 1.72 to 3.35 µm and good stability with surface charge of -42.6 and polydispersity index (PDI) of 0.45. The uncoated spray-dried C. nutans (control) exhibited wrinkle surface and irregular morphology with small particle size of 1.24 µm but poor stability with zeta potential value of -10.2 and PDI value of 0.86 which indicate that coagulation and flocculation will occur. The antioxidant release studies of coated spray-dried C. nutans in simulated gastric and intestinal fluids showed burst release of antioxidants in first 5 to 15 min and controlled release up to 240 min. In conclusion, the spray-dried C. nutans using κC/NaCMC microspheres is highly suitable for the formulation of herbal product.