HPLC/DAD, Antibacterial and Antioxidant Activities of Plectranthus Species (Lamiaceae) Combined with the Chemometric Calculations

Abstract

The increase in antibiotic resistance and the emergence of new bacterial infections have intensified the research for natural products from plants with associated therapy. This study aimed to verify the antibacterial and antioxidant activity of crude extracts of the genus Plectranthus species, being the first report on the modulation of aminoglycosides antibiotic activity by Plectranthus amboinicus extracts. The chemical composition was obtained by chemical prospecting and High-Performance Liquid Chromatography with diode arrangement detector (HPLC/DAD). The antibacterial activities of the extracts alone or in association with aminoglycosides were analyzed using the microdilution test. The antioxidant activity was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging. The phytochemical prospection allowed the flavonoids, saponins, tannins and triterpenoids to be identified. Quercetin, rutin, gallic acid, chlorogenic acid, caffeic acid, catechin, kaempferol, glycosylated kaempferol, quercitrin, and isoquercitrin were identified and quantified. The principal component analysis (PCA) observed the influence of flavonoids and phenolic acids from Plectranthus species on studied activities. Phytochemical tests with the extracts indicated, especially, the presence of flavonoids, confirmed by quantitative analysis by HPLC. The results revealed antibacterial activities, and synergistic effects combined with aminoglycosides, as well as antioxidant potential, especially for P. ornatus species, with IC50 of 32.21 µg/mL. Multivariate analyzes show that the inclusion of data from the antioxidant and antibacterial activity suggests that the antioxidant effect of these species presents a significant contribution to the synergistic effect of phytoconstituents, especially based on the flavonoid contents. The results of this study suggest the antibacterial activity of Plectranthus extracts, as well as their potential in modifying the resistance of the analyzed aminoglycosides.

New Specific α‐Glucosidase Inhibitor Flavonoid from Thymelaea tartonraira Leaves: Structure Elucidation, Biological and Molecular Docking Studies

“…Several studies have reported that the structure of flavonoids structure is directly related to their capacity to reduce metals or to trap free radicals. It is affected by the number and positions of the hydroxy groups (−OH) [16] . Herein, compound 4 shows the highest antioxidant power due to the four hydroxy groups presented in its structure.…”

“…It is affected by the number and positions of the hydroxy groups (À OH). [16] Herein, compound 4 shows the highest antioxidant power due to the four hydroxy groups presented in its structure. Moreover the presence of an α,β-unsaturated group at C ring increases this activity.…”

Mechanistic insight into the synergistic antimicrobial potential of Fagonia indica Burm.f. extracts with cefixime

“…In a prior study, chemical analyses of species extracts from the Plectranthus genus revealed that chlorogenic acid is predominant in EELPa, while caffeic acid is the most prevalent compound in EELPb and EELPo. All these species demonstrated antibacterial efficacy against both Gram-positive and Gram-negative bacteria, indicating their potential for combating bacterial infections due to the presence of these chemicals ( Rodrigues et al, 2021 ).Additionally, other studies found that gallic acid and caffeic acid have the ability to reverse the resistance phenotype of Staphylococcus aureus, with caffeic acid efficiently inhibiting bacterial pumps in silico ( Dos Santos et al, 2018 , Lima et al, 2016 ). The presence of quercetin also exhibited enhanced antibacterial activity against Staphylococcus aureus ( Dos Santos et al, 2021 ).…”

Influence of methanolic extracts from seeds and pulp of Annona squamosa L. on osmotic and morphological fragility in human erythrocytes

“…Phenolic compounds are the result of secondary metabolism in plants and are largely responsible for the antioxidant characteristics of a given extract ( Rodrigues et al, 2021 ). The presence of antioxidant compounds is important in extracts with pharmacological potential as it maintains the balance between pro and antioxidant substances.…”