Essential Oils from Piper caldense C. DC. and Piper xylosteoides (Kunth) Steud.: Seasonal Variation of the Chemical Composition and Antimicrobial Activity.

The essential oils (EOs) chemical composition can be affected by several environmental factors, impacting their desired biological activities. In this sense, this work aimed to evaluate the seasonal variation of the chemical composition and antimicrobial activity of Piper caldense and Piper xylosteoides leaves EOs. Their chemical composition was determined by GC/MS and GC-FID analyses, resulting in the identification of eighty compounds. P. caldense EOs were mainly consisted of sesquiterpene hydrocarbons, whereas in P. xylosteoides EOs, monoterpene hydrocarbons were predominant. EOs from both species strongly inhibited B. subtilis (MIC=0.25 mg mL-1 ), while only P. caldense EOs showed strong activity against S. aureus (MIC=0.50 mg mL-1 ). P. caldense spring EO showed the broadest spectrum of antimicrobial action amongst all samples. For each species, PCA seasonally differentiated EOs chemical composition. In addition, as expected, PCA of all samples showed a distinction between the two species. This study has successfully demonstrated the importance of evaluating the seasonal variation of EOs chemical composition and antimicrobial activity in obtaining a product with the desired properties.

Gas chromatography coupled to mass spectrometry (GC-MS) characterization and evaluation of antibacterial bioactivities of the essential oils from Piper arboreum Aubl., Piper aduncum L. e Piper gaudichaudianum Kunth.

The objective of this study was to determine the chemical profile and to evaluate the antibacterial activity of the essential oils of Piper species and modulation of the antibiotic activity, using the microdilution method to determine the minimum inhibitory concentration. The chemical components were characterized by gas chromatography coupled to mass spectrometry, which revealed ß-copaen-4-α-ol (31.38%), spathulenol (25.92%), and germacrene B (21.53%) as major constituents of the essential oils of Piper arboreum, Piper aduncum, and Piper gaudichaudianum, respectively. The essential oils analyzed in this study did not present a clinically relevant activity against standard and multiresistant Escherichia coli. However, in the case of multiresistant Staphylococcus aureus, there was a significant activity, corroborating with reports in the literature, where Gram-positive bacteria are more susceptible to antimicrobial activity. The essential oils modulated the effect of the antibiotics norfloxacin and gentamicin, having on the latter greater modulating effect; however, for erythromycin, no statistically significant effect was observed. In conclusion, the results obtained in this study demonstrated that the essential oils of the analyzed Piper species present an inhibitory effect against S. aureus and modulate antibiotic activity, most of which presents synergistic activity.

Photoinduced Antibacterial Activity of the Essential Oils from Eugenia brasiliensis Lam and Piper mosenii C. DC. by Blue Led Light.

The objective of this work was to evaluate the phytochemical composition and the antibacterial and antibiotic-modulating activities of the essential oils of Eugenia brasiliensis Lam (OEEb) and Piper mosenii C. DC (OEPm) singly or in association with blue LED (Light-emitting diode) light. The antibacterial and antibiotic-modulatory activities of the essential oils on the activity of aminoglycosides were evaluated to determine the minimum inhibitory concentration (MIC, µg/mL) in the presence or absence of exposure to blue LED light. The chemical analysis showed α-pinene and bicyclogermacrene as major constituents of OEPm, whereas α-muurolol was the main compound of OEEb. Both OEEb and OEPm showed MIC ≥ 512 µg/mL against the strains under study. However, the association of these oils with the blue LED light enhanced the action of the aminoglycosides amikacin and gentamicin. In conclusion, the association of aminoglycosides with the blue LED light and essential oils was effective against resistant bacteria.

Effect of the essential oils from Piper sp. and blue led lights in the enhancement of the antibiotic activity of drugs against mdr bacterial strains.

The indiscriminate use of antibiotics has made bacterial resistance an important public health problem, since many antibiotics have become ineffective. Phototherapy can be considered an alternative to reduce the abusive use of antimicrobials, thus impacting microbial resistance. The objective of this study was to determine the chemical profile and to evaluate the effect of blue LED lights on the antibacterial activity of essential oils from Piper species, as well as their aminoglycoside antibiotic activity modulation using the microdilution method to determine the Minimum Inhibitory Concentration (MIC). The antibiotic activity modulating effect of these oils was also determined using the broth microdilution method with 96-well plates which were exposed to LED light for 20 min. Chemical components were characterized by gas chromatography coupled to mass spectrometry, revealing ß-copaen-4-α-ol, germacrene A and germacrene B as major essential oil constituents for Piper arboreum (OEPar), Piper aduncum (OEPad) and Piper gaudichaudianum (OEPg), respectively. OEPar obtained a MIC of 512 µg/mL against Staphylococcus aureus and a MIC ≥ 1024 µg/mL against Escherichia coli. OEPad and OEPg showed MIC values ≥ 1024 µg/mL against the utilized strains. The essential oils modulated the effect of the antibiotics amikacin and gentamicin, with this effect being potentiated when exposed to blue LED. The blue LED light in the absence of the essential oil also showed an ability to modulate aminoglycoside antibiotic activity in this study, presenting mostly synergistic effects. In conclusion, the results obtained in this study demonstrate that photodynamic therapy using blue LED light interferes with the antibacterial action of P. arboreum, P. aduncum and P. gaudichaudianum essential oils and aminoglycoside antibiotic activity.