Comparative Antioxidant, Antibacterial, and Antidiabetic Activities of in Vitro-Grown Callus and Wild-Grown Various Parts of Piper longum L.

Piper longum L. is a tropical and subtropical medicinal plant that has been used as antidiabetic, diarrhea, stomachache, cough, asthma, and bronchitis since ancient times. The in vitro-grown callus from the leaf, however, has not been tested and utilized for any of these conditions. Thus, this research pursues to assess the comparative study of antioxidant, antibacterial, and antidiabetic activities of in vitro-grown callus and various parts of Piper longum-grown in the wild. The antioxidant activity of crude extracts and the fractions were determined by DPPH (1,1-diphenyl-2-picrylhydrazyl) free-radical scavenging assay, the antibacterial activity by agar-well diffusion method, and antidiabetic activity by α-amylase and α-glucosidase inhibition assay. In addition, the total phenol content (TPC) and total flavonoid contents (TFC) were calculated using Folin-Ciocalteau reagent and aluminum chloride complex-forming assay respectively. The highest antioxidant activity (IC50=134.81±1.16 µg/mL), TPC (41.22±0.50 mg of GAE/g dry weight), and TFC (73.41±0.53 mg of QE/g dry weight) were obtained in the dichloromethane (DCM) fraction of root than other crude extracts and fractions. The DCM fractions of root exhibited the minimum inhibitory concentration (MIC) at 5.0 mg/mL and minimum bactericidal concentration (MBC) of 8.35 mg/mL to the Staphylococcus aureus. Moreover, the DCM fraction of root showed the highest α-amylase and α-glucosidase inhibition (IC50=365.21±31.02 and 489.07±27.96 µg/mL) than other crude extracts and fractions. To the best of our information, comparative antioxidant (IC50=206.61±0.64 µg/mL), antibacterial (suppressed 80% of tested bacteria), and antidiabetic (IC50=1165.15±15.63 and 1304.76±12.43 µg/mL) properties of the in vitro-grown callus were recorded for the first time in P. longum, and were found to be comparative to those of the wild-grown parts. These results showed that wild-grown P. longum roots, particularly the DCM fraction, could be an important source of natural antioxidants, antimicrobials, and antidiabetics for better curative uses than other wild-grown parts and in vitro-grown callus. In vitro-grown callus, however, could be used as a natural drug source and used to conserve P. longum in its natural habitats in the future.