Antimicrobial Activity of Psidium guajava Aqueous Extract against Sensitive and Resistant Bacterial Strains

Abstract

The inappropriate use of antimicrobials, along with environmental conditions, can lead to the emergence of resistant microorganisms. The use of phytopharmaceuticals and herbal medicines has a positive impact and represents a promising alternative. Psidium guajava extracts have been widely reported to have antimicrobial potential; however, studies reporting their activity against resistant bacterial strains are scarce. Because of the emerging resistance, the aim of this study was to analyze the antimicrobial capacity of the aqueous extract of guava leaves against wild-type and resistant bacterial strains. The aqueous extract obtained from the leaves of P. guajava was evaluated by HPLC for the content of total phenolics and tannins, antioxidant activity, and chemical composition. The antimicrobial activity of the extracts was analyzed by the disk diffusion and broth microdilution methods. The results of the chemical analysis of the extracts showed total phenolics content of 17.02 ± 6.87 mg/g of dry extract, total tannin content of 14.09 ± 1.20 mg of tannic acid equivalents/g of dry extract, and moderate antioxidant capacity with an EC50 value of 140 µg/mL. Flavonoids are the major compounds (rutin, hesperidin, and quercetin), followed by phenolic acids. Disk diffusion test results showed the presence of inhibition halos for Gram-positive bacteria (Staphylococcus aureus, sensitive and resistant; Staphylococcus pseudintermedius, sensitive and resistant; and Streptococcus spp., beta-hemolytic), while for Gram-negative bacteria (Escherichia coli, sensitive and resistant), there was no inhibition in the tested concentration range. The Minimal Inhibitory Concentration was 6.8 mg/mL for all Gram-positive strains evaluated. The present study demonstrated the antimicrobial activity of the aqueous extract of P. guajava against sensitive and resistant Gram-positive bacteria. The better antimicrobial activity found in the present study compared with previously reported activity should be highlighted and may be related to the higher concentration of total phenolics present in the tested extract. Moreover, the content of tannins found suggests a species with high quality that produces tannins. These new findings suggest an innovative profile regarding therapeutic resources that can be adopted to combat resistant microbial strains.

Nutritional Composition, Mineral Profiling, In Vitro Antioxidant, Antibacterial and Enzyme Inhibitory Properties of Selected Indian Guava Cultivars Leaf Extract

“…Previously, the antibacterial activity of the methanolic leaf extract of guava was reported with the mean zone of inhibition ranging from 8.27 ± 0.44 to 12.3 ± 0.78 mm [4] whereas in the present study, the mean zone of inhibition ranged from 17.67 ± 0.57 to 25.66 ± 0.57 mm which is comparatively higher than the previous reports. To support our study, Pereira et al [49] reported that the methanolic leaf extract of P. guajava had greater antibacterial activity against Gram-positive and Gram-negative bacterial strains and recorded the highest zone of inhibition with 21.0 ± 2.0 mg/mL against the bacterial strain Streptococcus beta-hemolytic. Previously, the antibacterial activity of the methanolic leaf extract of guava was reported with the mean zone of inhibition ranging from 8.27 ± 0.44 to 12.3 ± 0.78 mm [4] whereas in the present study, the mean zone of inhibition ranged from 17.67 ± 0.57 to 25.66 ± 0.57 mm which is comparatively higher than the previous reports.…”

“…Previously, the antibacterial activity of the methanolic leaf extract of guava was reported with the mean zone of inhibition ranging from 8.27 ± 0.44 to 12.3 ± 0.78 mm [4] whereas in the present study, the mean zone of inhibition ranged from 17.67 ± 0.57 to 25.66 ± 0.57 mm which is comparatively higher than the previous reports. To support our study, Pereira et al [49] reported that the methanolic leaf extract of P. guajava had greater antibacterial activity against Gram-positive and Gram-negative bacterial strains and recorded the highest zone of inhibition with 21.0 ± 2.0 mg/mL against the bacterial strain Streptococcus beta-hemolytic.…”

“…The free radical scavenging capacity of guava leaf extracts was scrutinized by (2,2'azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)) (ABTS) radical cation decolorization assay [49] with BHT as a reference drug. The calculated values were denoted as IC 50 values and the scavenging capacity of the samples was calculated using the following equation: % Inhibition = [(Acontrol − Asample)/Acontrol] × 100…”

Hydroalcoholic extract of Psidium guajava plant and bone marrow cells: examination and analysis of effects

“…Moreover, it is perceived to be effective in hematopoiesis through increasing the number of red blood cells and bone marrow erythroid cells. Examining the antioxidant activity of guava hydroalcoholic extract shows that this extract plays a great role in trapping free radicals and preventing anemia [30][31][32].…”

“…Evidence suggests that, since guava leaf hydroalcoholic extract is rife with flavonoids, tannins, ellagic acid, triterpenes and quercetin, it can provide favorable conditions for the growth and differentiation of stem cells into hematopoietic cells and help in the regeneration of blood tissue. These compounds can protect cell membranes, including red blood cell membranes, from damage caused by free radicals, prevent their destruction, and hence increase their count in the blood [30][31][32].…”