Chemical analysis and bioactivity evaluation of the stem of Rheum tanguticum

Abstract

Rhubarb (Dahuang in Chinese), belongs to the family Polygonaceae, genus Rheum, has been employed as a traditional Chinese medicinal material for a long time. Rheum officinale, R. palmatum, R. tanguticum, R. rhaponticum, R. ribes, R. franzenbachii, and R. rhabarbarum have been reported to possess many pharmacological active substances that are used to treat diseases. The petioles of R. rhabarbarum, R. ribes, R. rhaponticum are well-known vegetables in some regions of the world. Based on this folk application and active ingredients that may be present in stems, the present study was conducted to analyze the content of nutritional components and active secondary metabolism components, and evaluate the antimicrobial activity and antioxidant activity with prepared solvent extracts. Methods published by the Association of Official Analytical Chemistry (AOAC) was used to determine the total protein, crude fat, crude fiber, vitamin C, ash, and moisture contents. The results showed that the inflorescence stem of R. tanguticum contained a higher content of crude fiber (89.14%) and vitamin C (16.96%). The content of total protein and crude fat was 8.49% and 1.34% respectively. The results showed that the DPPH Radical Scavenging Activity of the extract had a concentration-dependent effect. The highest activity (83.4%) of the methanol extract sample was recorded at 1.0 mg/mL and the lowest activity, 15.56%, was recorded at 0.2 mg/mL. 0.485 mg/mL was needed to achieve a 50% toxicity. The flavonoid and total phenolic contents of the inflorescence stem of R. tanguticum were found to be 0.022 mg/g and 4.138 mg/g respectively. A concentration of 10 mg/mL successfully inhibited the growth of the pathogenic microorganisms, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis using the paper disc diffusion method. In summary, the results of this study confirm that the inflorescence stem of R. tanguticum contains some rich nutritional components and bioactive secondary metabolism components that are beneficial for human health as edible parts or processed products. The results of bioactivity evaluation in this study also showed that the inflorescence stem of R. tanguticum could be developed natural antioxidant and antibacterial agent as a potential resource. This may possibly provide a feasible solution for non-medicinal parts utilization.