Foods rich in antioxidants play an essential role in the prevention of diseases. The present study compared contents of phenolics, vitamin C, anthocyanin and antioxidant activity of 11 fresh exotic fruits, cultivated in the northeastern part of Brazil. The antioxidant activities were evaluated using two antioxidant systems 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), expressed as TEAC (Trolox Equivalent Antioxidant Capacity) and VCEAC (Vitamin C Equivalent Antioxidant Capacity) values. The results indicated that the above fruits, such as murici and mangaba, were good sources of antioxidants. The phenolic contents showed positive correlations with total antioxidant by ABTS (R = 0.94, P ≤ 0.001) and DPPH (R = 0.88, P ≤ 0.001) assays. However, this correlation was not noticed when examining vitamin C and anthocyanins contents. The 11 fruits studied had comparable antioxidant activity in both, ABTS and DPPH assays. These methods are recommended as useful tools for the evaluation of the total activity antioxidant in fruits. Our results indicated promising perspectives for the development and usage of fruits species studied with considerable levels of antioxidant activity.

Dental caries and periodontal disease are associated with oral pathogens. Several plant derivatives have been evaluated with respect to their antimicrobial effects against such pathogenic microorganisms. Lippia sidoides Cham (Verbenaceae), popularly known as "Alecrimpimenta" is a typical shrub commonly found in the Northeast of Brazil. Many plant species belonging to the genus Lippia yield very fragrant essential oils of potential economic value which are used by the industry for the commercial production of perfumes, creams, lotions, and deodorants. Since the leaves of L. sidoides are also extensively used in popular medicine for the treatment of skin wounds and cuts, the objective of the present study was to evaluate the composition and antimicrobial activity of L. sidoides essential oil. The essential oil was obtained by hydro-distillation and analyzed by GC-MS. Twelve compounds were characterized, having as major constituents thymol (56.7%) and carvacrol (16.7%). The antimicrobial activity of the oil and the major components was tested against cariogenic bacterial species of the genus Streptococcus as well as Candida albicans using the broth dilution and disk diffusion assays. The essential oil and its major components thymol and carvacrol exhibited potent antimicrobial activity against the organisms tested with minimum inhibitory concentrations ranging from 0.625 to 10.0 mg/mL. The most sensitive microorganisms were C. albicans and Streptococcus mutans. The essential oil of L. sidoides and its major components exert promising antimicrobial effects against oral pathogens and suggest its likely usefulness to combat oral microbial growth.

Ursolic acid, an important bioactive compound, was isolated from ethanol extract of aerial parts of Sambucus australis. In order to develop bioactive ursolic acid derivatives, two semi-synthetic compounds were obtained through modification at C-3. The antibacterial activity of the ursolic acid and its derivatives was investigated. The microdilution method was used for determination of the minimal inhibitory concentration (MIC), against twelve bacterial strains. The influence of ursolic acid and its derivatives on the susceptibility of some bacterial pathogens to the aminoglycosides antibiotics neomycin, amikacin, kanamycin and gentamicin was evaluated. The most representative synergistic effect was observed by 3β-formyloxy-urs-12-en-28-oic acid at the concentration of 64 μg/mL in combination with kanamycin against Escherichia coli (27), a multidrugresistant clinical isolate from sputum, with reduction of MIC value from 128 μg/mL to OPEN ACCESSMolecules 2014, 19 1318 8 μg/mL. Ursolic acid and its derivatives were examined for their radical scavenger activity using the DPPH assay, and showed significant activity.

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Among ten essential oils submitted to antimicrobial evaluation, the oil from Lippia sidoides exhibited the highest and broadest activity against fungi and bacteria. Lippia oil was active against all test bacteria, including moderate activity against the Gram-negative bacteria Pseudomonas aeruginosa and Escherichia cofi, and all test fungi, including yeasts, a dermatophyte, and filamentous fungi.

Currently, there is renewed interest in plant-based medicines and functional foods for the prevention and cure of obesity and its associated risk of cardiovascular disease and metabolic syndrome. In the search for potential anti-obesity compounds from natural sources, the effects of ursolic acid (UA), a pentacyclic triterpenoid widely found in medicinal herbs and fruits, was evaluated for its effects on blood glucose, lipids, and abdominal fat deposition in mice fed a high-fat diet (HFD). Adult male Swiss mice treated or not with UA (0.05%, 50 mg/L, in drinking water) were fed HFD for 15 weeks. A sibutramine (SIB)-treated group (0.05% in drinking water) was included as the positive control. Weekly body weights and food and water consumption were measured, and at the end of the study period, the levels of blood glucose and lipids, the plasma hormones insulin, ghrelin, and leptin, and the abdominal fat accumulation were analyzed. Mice treated with UA and fed HFD showed significantly (P<.05) decreased body weights, visceral adiposity, and levels of blood glucose and plasma lipids relative to their respective controls not fed UA. Also, a significant increase was observed in plasma leptin with a decrease in ghrelin, as well as of amylase and lipase activities. The SIB-treated group also manifested effects similar to those of UA except for the blood glucose level, which was not different from the HFD control. These findings suggest that UA ameliorates abdominal adiposity and decreases the levels of blood glucose and plasma lipids in mice and thus manifests an anti-obesity potential through absorptive and metabolic targets.

Eugenol is the major component of clove essential oil and has demonstrated relevant biological potential with well-known antimicrobial and antioxidant action. Therefore, this work carried out the synthesis, purification, characterization, and evaluation of the antioxidant and antibacterial potential of 19 eugenol derivatives. The derivatives were produced by esterification reactions in the hydroxyl group (−OH) of eugenol with different carboxylic acids and also by addition reactions in the double bond of the allyl group. The derivatives had a promising antibacterial potential, including a lower minimum inhibitory concentration of 500 μg/mL than eugenol (1000 μg/mL). In addition, the derivatives were active against bacterial strains (Escherichia coli, Staphylococcus aureus) that eugenol itself showed no activity, thus increasing the spectrum of antibacterial action. As for the antioxidant activity, it was observed that the derivatives that involved esterification reactions in the hydroxyl group (−OH) of the eugenol molecule’s phenol resulted in a significant reduction of the antioxidant action (IC50 > 100 μg/mL) when compared with the eugenol precursor molecule (IC50 = 4.38 μg/mL). On the other hand, the structural changes located in the double bond affected much more smoothly the capacity of capturing radicals than the starting molecule, also being obtained derivatives with proximal antioxidant capacity (IC50 = 19.30 μg/mL) to commercial standards such as Trolox (IC50 = 16.00 μg/mL).Electronic supplementary materialThe online version of this article (10.1186/s13065-018-0407-4) contains supplementary material, which is available to authorized users.

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