Phytochemical characterisation and bioprospection for antibacterial and antioxidant activities of Lippia alba Brown ex Britton & Wilson (Verbenaceae)

Lippia alba-a potential bioresource for the management of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), a threat to maize production systems, is a polyphagous pest of global significance. There is no registered bioinsecticide of botanical origin to provide green remedy against this pest of concern. The present study reports for the first time the potency of the polar and non-polar bioinsecticidal leads sourced from Lippia alba (Mill.) N.E. Br. leaves. Shade-dried leaves of L. alba were extracted and evaluated; based on preliminary bioassay, the ethyl acetate leaf extract of L. alba (LEAE) was found to be the most potent against FAW in the in vitro and in vivo studies. Ultraperformance liquid chromatography-quadrupole time-of-flight-mass spectrometric (UPLC-QToF-MS) analysis of LEAE revealed the rich chemical profile of 28 compounds, dominated by flavones, namely, naringenin, trihydroxy-dimethoxy flavone, and dihydroxy-trimethoxy flavone. Among others, glycosides, such as clerodendrin, calceolarioside E, forsythoside B, geniposide, and martynoside, and glucuronides, such as luteolin-7-diglucuronide, tricin-7-O-glucuronide, and luteolin-7-O-glucuronide, were also identified. LEAE exhibited exceptionally high in vitro [LC50 = 6,900 parts per million (ppm)] and in vivo (computed as damage score on a scale of 1-9) insecticidal activity against S. frugiperda, with no phytotoxicity at a dose as high as 20 times of LC50. LEAE also exhibited significant antifeedant, ovicidal, and growth regulatory activity at the 70-16,000 ppm (w/v) concentration range. In silico assessment revealed strong binding of martynoside, calceolarioside E, and forsythoside B with acetylcholinesterase-, sodium-, and chloride-dependent γ-aminobutyric acid (GABA) receptor and ryanodine receptor, respectively, facilitated by hydrogen bonds (conventional and C-H bonds) stabilized by hydrophobic pi-sigma, pi-pi stacked, pi-alkyl, and alkyl interactions. The present study established L. alba as a potential bioresource and secondary metabolite enriched LEAE as bioinsecticide for further product development.

Biological effects of Lippia alba essential oil against Anopheles gambiae and Aedes aegypti

The management of mosquito resistance to chemical insecticides and the biting behaviour of some species are motivating the search for complementary and/or alternative control methods. The use of plants is increasingly considered as a sustainable biological solution for vector control. The aim of this study was to evaluate the biological effects of the essential oil (EO) of Lippia alba harvested in Abidjan (Côte d'Ivoire) against Anopheles gambiae and Aedes aegypti mosquitoes. Phytochemical compounds were identified by GC-MS. Knockdown and mortality were determined according to the WHO test tube protocol. Contact irritancy was assessed by observing the movement of mosquitoes from a treated WHO tube to a second untreated tube. Non-contact repellency was assessed using a standardised high-throughput screening system (HITSS). Blood meal inhibition was assessed using a membrane feeding assay treated with EO. The EO was identified as the citral chemotype. The EO gave 100% KD60 in both species at a concentration of 1%. Mortalities of 100% were recorded with An. gambiae and Ae. aegypti at concentrations of 1% and 5% respectively. The highest proportions of females escaping during the contact irritancy test were 100% for An. gambiae at 1% concentration and 94% for Ae. aegypti at 2.5% concentration. The 1% concentration produced the highest proportions of repelled mosquitoes in the non-contact repellency tests: 76.8% (An. gambiae) and 68.5% (Ae. aegypti). The blood meal inhibition rate at a dose of 10% was 98.4% in Ae. aegypti but only 15.5% in An. gambiae. The citral chemotype of L. alba EO has promising biological effects in both species that make it a potentially good candidate for its use in mosquito control. The results obtained in this study encourage the further evaluation of L. alba EOs from other localities and of different chemotypes, under laboratory and field conditions.

Antibacterial Activity and Anxiolytic Effect in Adult Zebrafish of Genus Lippia L. Species

Species belonging to the genus Lippia are used worldwide as foods, beverages, and seasonings. Studies have demonstrated that these species have antioxidant, sedative, analgesic, anti-inflammatory, and antipyretic activities. This work aimed to evaluate the antibacterial activity and anxiolytic effect by different pathways of essential oils and ethanolic extracts of three species of Lippia (Lippia alba, Lippia sidoides, and Lippia gracilis). The ethanolic extracts were characterized by HPLC-DAD-ESI-MSⁿ and their phenolics were quantified. The antibacterial activity was evaluated by determining the minimal inhibitory concentration and modulation of antibiotic activity, and toxic and anxiolytic effects were evaluated in the zebrafish model. The extracts showed compositions with a low ratio and shared compounds. L. alba and L. gracilis showed higher amounts of phenols and flavonoids, respectively. All extracts and essential oils presented antibacterial activity, especially those obtained from L. sidoides. On the other hand, L. alba extract presented the most significant antibiotic-enhancing effect. The samples were not toxic after 96 h of exposure, but showed an anxiolytic effect through modulation of the GABA_A receptor, while L. alba extract acted via modulation of the 5-HT receptor. This new pharmacological evidence opens horizons for therapeutic approaches targeting anxiolytic and antibacterial therapies and food conservation using these species and their constituents.

Effect of Lippia alba (Mill.) N.E. Brown Essential Oil on the Human Umbilical Artery

Lippia alba is popularly known as lemon balm, with its essential oil (EO) cited for displaying antimicrobial, sedative, and vasorelaxant effects. Yet, its action on isolated human vessels has not been described in the literature. Thus, we evaluated the vasorelaxant effect of essential oil of L. alba (EOLa) on human umbilical arteries (HUA) isolated in organ baths. HUA rings were isolated, subjected to contractions induced by potassium chloride (KCl), serotonin (5-HT), or histamine (HIST) to record the isometric tension, and then treated with EOLa (30-1000 µg/mL). The EOLa showed a more prominent inhibitory effect on the pharmacomechanical coupling contraction via HIST with an EC₅₀ value of 277.1 ± 8.5 µg/mL and maximum relaxant effect at 600 µg/mL. The addition of tetraethylammonium (TEA) or 4-aminopyridine (4-AP) in HUA preparations did not inhibit EOLa total relaxant effect at 1000 µg/mL. In the presence of gliblenclamide (GLI), the oil relaxed the HUA rings by 90.8% at maximum concentration. The EOLa was also investigated for its effects on voltage-operated calcium channels (VOCCs), where the HUA preincubation with this oil at 1000 μg/mL inhibited BaCl₂ (0.1-30 mM)-induced contractions. This study demonstrates for the first time that EOla has a vasorelaxant effect on HUA and its particular blockade of VOCCs.

Ethnomedicinal Plants Used for the Treatment of Cardiovascular Diseases by Healers in the Southwestern State of Paraná, Brazil, and Their Validation Based on Scientific Pharmacological Data

Cardiovascular diseases are responsible for high morbidity and mortality rates worldwide. Among treatment options, medicinal plants are frequently used, especially in developing countries, such as Brazil. Despite social development that has been observed in the last decades, the use of medicinal plants is still driven by popular knowledge, especially by healers. The present study sought to identify medicinal species that are used for the treatment of cardiovascular diseases by healers in the microregion of Francisco Beltrão, Paraná, Brazil. The snowball technique was used to select informants, and data were collected through interviews. The research was performed in two stages: (1) a structured interview and (2) the collection and botanical identification of the species that were mentioned by the healers. Medicinal plants were classified into the following categories of cardiovascular agents: hypotensive and antihypertensive agents, lipid-lowering agents, diuretic agents, and cardiotonic agents. To analyze the data, the frequency was determined, Spearman correlations were calculated, and the informant consensus factor (ICF) and use value were obtained. Some characteristics, such as female gender and old age, were associated with knowledge about medicinal plants. Overall, 77 different species and 149 medicinal uses were cited by the healers. With regard to categories of use, the highest number of species was found among lipid-lowering plants, and the highest ICF was found for species that are used as cardiotonics. Moreover, a literature review indicated that among the cited species, several still lack studies that have proven their effects on the cardiovascular system. The traditional use of medicinal plants for the treatment of cardiovascular diseases is broad in the study regions. The present results are important for clarifying popular knowledge in this region and providing a framework for selecting species with potential for the development of new pharmacological studies.

Antimicrobial Activity of Schinopsis brasiliensis Engler Extract-Loaded Chitosan Microparticles in Oral Infectious Disease

Enterococcus faecalis infections represent a health concern, mainly in oral diseases, in which treatments with chlorhexidine solution (0.2%) are often used; however, it presents high toxicity degree and several side effects. Based on this, the use of natural products as an alternative to treatment has been explored. Nonetheless, plant extracts have poor organoleptic characteristics that impair theirs in natura use. Therefore, this work aimed to evaluate the analytical profile, biological activity, and cytotoxicity in vitro of S. brasiliensis-loaded chitosan microparticles (CMSb) produced using different aspersion flow rates. The analytical fingerprint was obtained by FTIR and NIR spectra. Principal components analysis (PCA) was used to verify the similarity between the samples. The crystallinity degree was evaluated by X-ray diffraction (XRD). Phytochemical screening (PS) was performed to quantify phytocompounds. Antimicrobial activity was evaluated by minimum inhibitory concentration (MIC). Antibiofilm activity and bactericidal kinetics against E. faecalis (ATCC 29212 and MB 146-clinical isolated) were also assessed. The hemolytic potential was performed to evaluate the cytotoxicity. Data provided by FTIR, NIR, and PCA analyses revealed chemical similarity between all CMSb. Furthermore, the results from XRD analysis showed that the obtained CMSb present amorphous characteristic. Tannins and polyphenols were accurately quantified by the PS, but methodology limitations did not allow the flavonoid quantification. The low hemolytic potential assay indicates that all samples are safe. Antimicrobial assays revealed that CMSb were able to inhibit not only the E. faecalis ATCC growth but also the biofilm formation. Only one CMSb sample was able to inhibit the clinical strain. These results highlighted the CMSb antimicrobial potential and revealed this system as a promising product to treat infections caused by E. faecalis.

Pharmacologic potential of new nitro-compounds as antimicrobial agents against nosocomial pathogens: design, synthesis, and in vitro effectiveness

Nosocomial infections are an important cause of morbi-mortality worldwide. The increase in the rate of resistance to conventional drugs in these microorganisms has stimulated the search for new therapeutic options. The nitro moiety (NO₂) is an important pharmacophore of molecules with high anti-infective activity. We aimed to synthesize new nitro-derivates and to evaluate their antibacterial and anti-Candida potential in vitro. Five compounds [3-nitro-2-phenylchroman-4-ol (3); 3-nitro-2-phenyl-2H-chromene (4a); 3-nitro-2-(4-chlorophenyl)-2H-chromene (4b); 3-nitro-2-(4-fluorophenyl)-2H-chromene (4c), and 3-Nitro-2-(2,3-dichlorophenyl)-2H-chromene (4d)] were efficiently synthesized by Michael-aldol reaction of 2-hydroxybenzaldehyde with nitrostyrene, resulting in one β-nitro-alcohol (3) and four nitro-olefins (4a-4d). The antibacterial and anti-Candida potentials were evaluated by assaying minimal inhibitory concentration (MIC), minimum fungicidal concentration (MFC), and minimum bactericidal concentration (MBC). Mono-halogenated nitro-compounds (4b and 4c) showed anti-staphylococcal activity with MIC values of 15.6-62.5 μg/mL and MBC of 62.5 μg/mL. However, the activity against Gram-negative strains was showed to be considerably lower and our data suggests that this effect was associated with the outer membrane. Furthermore, nitro-compounds 4c and 4d presented activity against Candida spp. with MIC values ranging from 7.8-31.25 μg/mL and MFC of 15.6-500 μg/mL. In addition, these compounds were able to induce damage in fungal cells increasing the release of intracellular material, which was associated with actions on the cell wall independent of quantitative changes in chitin and β-glucan. Together, these findings show that nitro-compounds can be exploited as anti-staphylococcal and anti-Candida prototypes.

Allelopathic effect of the ethanol extract and fractions of the aerial parts of Lippia alba (Verbenaceae)

Lippia alba, belonging to the Verbenaceae family, is one of the most commonly utilized medicinal plants in folk medicine. The allelopathic activity was assessed using seeds of Lactuca sativa (lettuce) and Allium cepa (onion) by assessing the growth of the radicle and hypocotyl. The tests showed allelopathic efficiency in inhibiting the growth of lettuce and onion seeds. The best results for allelopathic activity were presented by the dichloromethane (DCM) fraction of the fresh plant, which inhibited radicle (23.04-100% lettuce and 64.17-66.36% onion) and hypocotyl (16.77-100% lettuce and 65.10-69.43% onion) formation, and as well as the DCM fraction of the dry plant, which also inhibited radicle (30.74-82.83% lettuce and 63.50-93.67% onion) and hypocotyl (24.12-70% lettuce and 69.07-79.95% onion) formation. Based on these results, it was found that the aerial parts of L. alba are rich in bioactive substances, suggesting the possibility of using of L. alba as a natural herbicide.