Putative mycobacterial efflux inhibitors from the seeds of Aframomum melegueta

Four pairs of tautomers from rhizomes of Acorus calamus and fruits of Cornus officinalis

A pair of new guaiane-type sesquiterpene tautomers (1) was isolated from rhizomes of Acorus calamus. Meanwhile, three pairs of known compounds, including a pair of dihydroflavone glycoside tautomers (2), a pair of 4-hydroxybenzoic acid ester glycoside tautomers (3), as well as a pair of secoiridoid glycoside tautomers (4) were isolated from fruits of Cornus officinalis. Their structures were elucidated by extensive spectroscopic and computational methods. Furthermore, the tautomeric mechanisms were discussed.

Bioprospecting for Anti-COVID-19 Interventions From African Medicinal Plants: A Review

The emergence of the novel coronavirus (SARS-CoV-2) that emanated from Wuhan in China in 2019 has become a global concern. The current situation warrants ethnomedicinal drug discovery and development for delivery of phytomedicines with potential for the treatment of COVID-19. The aim of this review is to provide a detailed evaluation of available information on plant species used in African traditional medicines with antiviral, anti-inflammatory, immunomodulatory, and COVID-19 symptoms relieving effects. Literature from scientific databases such as Scopus, PubMed, Google scholar, African Journals OnLine (AJOL), Science Direct, and Web of Science were used for this review. A total of 35 of the 38 reviewed plants demonstrated a wide range of antiviral activities. Bryophyllum pinnatum, Aframomum melegueta, Garcinia kola, Sphenocentrum jollyanum, Adansonia digitata, Sutherlandia frutescens, Hibiscus sabdariffa, Moringa oleifera, and Nigella sativa possess a combination of antiviral, immunomodulatory, anti-inflammatory, and COVID-19 symptoms relieving activities. Nine, 13, and 10 of the plants representing 23.7%, 34.2%, and 26.3% of the plants studied had antiviral activity with 3 other activities, antiviral activity with 2 other activities, and antiviral with one pharmacological activity alone, respectively. The plants studied were reported to be relatively safe at the subchronic toxicity level, except for 2. The study provides baseline information on the pharmacological activities, toxicity, and chemical components of 9 African medicinal plants with antiviral, immunomodulatory, anti-inflammatory, and symptoms relieving activities, thereby making the plants candidates for further investigation for effectiveness against COVID-19.

6-Gingerol and Semisynthetic 6-Gingerdione Counteract Oxidative Stress Induced by ROS in Zebrafish

6-Gingerol (1) is one of the major components in ginger and developing new synthetic methodologies could bring semisynthetic analogs with improved therapeutic properties. Towards this, multigram scale isolation of 6-gingerol with excellent purity was optimized using a simple and robust extraction, followed by column purification. Synthesis of 6-gingerdione, 7 from 6-gingerol was then achieved through selective -OTBDMS protection, DMP oxidation and deprotection reaction sequence for the first time. Compounds 1, 7 and 8 (dehydrozingerone) exhibited excellent cell-free antioxidant properties in DPPH, ABTS, superoxide radical scavenging assay and H2 O2 assay at 10-50 μM concentrations. The hemolytic study suggests that up to 50 μM, all three compounds did not exhibit toxicity to human erythrocytes. When H2 O2 treated zebrafish larvae groups (96hpf) were exposed to compounds 1, 7 and 8, it increases the SOD (19, 19.1 and 18.7 U/mg protein), CAT (18.1, 16.5, and 15.8 μmol/mg levels and decreases the lipid peroxidation level (13, 15 and 18 nmol/mg protein), respectively. In vivo ROS levels and degree of cell death were studied using DCFDA and Acridine orange assays. Compounds 1, 7 and 8 decreases the ROS and cell death level significantly. Taken together, compounds 1, 7 and 8 exhibit excellent antioxidant properties, counteract H2 O2 induced oxidative stress, reduces cell death in zebrafish larvae.

6-Paradol Acts as a Potential Anti-obesity Vanilloid from Grains of Paradise

SCOPE

Grains of Paradise (GOP), the seeds of Aframomum melegueta, has anti-obesity effects. However, the mechanisms underlying the effects remain unclear.

METHODS AND RESULTS

This study sets up to study the anti-obesity impact and homeostatic effects of 6-paradol, a major vanilloid found in GOP, and investigates the physiological outputs and the lipometabolism-related gene in fat and liver in high-fat-induced obese mice with a comparison with structurally similar vanilloids (6-gingerol and 6-shogaol). The vanilloids are synthesized in adequate quantities for performing animal experiments and orally administered to 6-week-old male mice over 2 weeks. This study found that 6-paradol decreased body weight gain and visceral and subcutaneous fats in 2 weeks, whereas 6-gingerol and 6-shogaol have no effect. Additionally, 6-paradol suppresses the hepatic cholesterol and triglyceride and significantly decreases the gene expression related to fatty acid synthesis, lipid transportation, and adipocyte differentiation in both liver and adipose tissue. Moreover, phosphorylation of AMP-activated protein kinase (AMPK) that greatly contributes to lipometabolism is promoted by 6-gingerol but not 6-paradol.

CONCLUSION

These results suggest that 6-paradol regulates several obesity-related genes in an AMPK-independent manner. Therefore, it could be the principal active vanilloid in GOP giving it anti-obesity properties with a different mechanism.

Spororrminone A and 2-epi-spororrminone A, two new chromones from an endolichenic fungus Sporormiella irregularis

Two new chromones, spororrminone A (1, (S)-5-hydroxy-2-methyl-4-oxo-2-((S)-5-oxotetrahydrofuran-2-yl)chroman-7-carboxylic acid) and 2-epi-spororrminone A (2, (R)-5-hydroxy-2-methyl-4-oxo-2-((S)-5-oxotetrahydrofuran-2-yl)chroman-7-carboxylic acid), were isolated from an EtOAc extract of an endolichenic fungal strain Sporormiella irregularis (No. 71-11-4-1). The structures of these compounds were identified by spectroscopic analyses. The absolute configuration of 1 was established by single-crystal X-ray diffraction. Spororrminone A (1) and 2-epi-spororrminone A (2) represent the first examples of 2-(5-oxotetrahydrofuran-2-yl) chromones with 7-carboxylic group.

Efficacy and Mechanisms of Flavonoids against the Emerging Opportunistic Nontuberculous Mycobacteria

Nontuberculous mycobacteria (NTM) are the causative agent of severe chronic pulmonary diseases and is accountable for post-traumatic wound infections, lymphadenitis, endometritis, cutaneous, eye infections and disseminated diseases. These infections are extremely challenging to treat due to multidrug resistance, which encompasses the classical and existing antituberculosis agents. Hence, current studies are aimed to appraise the antimycobacterial activity of flavonoids against NTM, their capacity to synergize with pharmacological agents and their ability to block virulence. Flavonoids have potential antimycobacterial effects at minor quantities by themselves or in synergistic combinations. A cocktail of flavonoids used with existing antimycobacterial agents is a strategy to lessen side effects. The present review focuses on recent studies on naturally occurring flavonoids and their antimycobacterial effects, underlying mechanisms and synergistic effects in a cocktail with traditional agents.

Two undescribed paradol-related specialized metabolites from Aframomum melegueta

Aframomum melegueta seeds are widely used as a spice in Africa. Two undescribed paradol-related compounds, (S)-9-hydroxy-[6]-paradol (1) and (9S)-3,9-dihydroxydihydro-[6]-paradol (2) together with eight reported constituents (3-10) were isolated and characterised from the methanol extract of A. melegueta seeds. Structure elucidation of these metabolites was achieved by means of NMR and mass spectroscopic data analyses. The absolute configuration of undescribed compounds (1 and 2) was determined using the modified Mosher's method.

Flavonoids as Novel Efflux Pump Inhibitors and Antimicrobials Against Both Environmental and Pathogenic Intracellular Mycobacterial Species

Therapeutic treatment options for opportunistic non-tuberculous mycobacterial (NTM) infection and/or serious mycobacterial infections such as tuberculosis (TB) and leprosy are limited due to the spread of antimicrobial resistance mechanism. Plant-derived natural compounds as prospective efflux pump inhibitors may present a promising adjunct to conventional chemotherapy by enhancing mycobacterial susceptibility to antibiotics. This study served to evaluate the antimicrobial and resistance-modifying profile of a range of plant-derived flavonoids against the mycobacterial model strains: M. smegmatis, M. aurum, and M. bovis BCG. The minimum inhibitory concentrations (MICs) of the compounds against the mycobacterial strains were determined using both agar dilution and broth dilution assays, while their efflux inhibitory activity was investigated via an ethidium bromide-based fluorometric assay. All compounds were screened for their synergistic effects with ethidium bromide (EtBr) and rifampicin (RIF) against M. smegmatis. Skullcapflavone II (5,2′-dihydroxy-6,7,8,6′-tetramethoxyflavone, 1) exerted potent antimicrobial activity against M. aurum and M. bovis BCG and considerably increased the susceptibility of M. smegmatis to EtBr and RIF. Nobiletin (5,6,7,8,3′,4′-hexamethoxyflavone, 2) was determined to be the most potent efflux-inhibitor in M. aurum and M. smegmatis. However, a connection between strong modulatory and putative efflux activity of the compounds could not be observed. Nevertheless, the results highlight two polymethoxyflavones, skullcapflavone II and nobiletin, with potent antimycobacterial and antibiotic resistance modulating activities as valuable adjuvants in anti-mycobacterial therapies.

A new cinnamamide derivative and two new β-carboline alkaloids from the stems of Picrasma quassioides

Picrasamide A (1), a new cinnamamide derivative, together with two new β-carboline alkaloids (2 and 3) and five known β-carboline alkaloids (4-8) were isolated from the stems of Picrasma quassioides (D. Don) Benn. Their structures were elucidated by detailed analyses of UV, IR, HRESIMS, and NMR data. Compound 1 was the first case of cinnamamide derivative from genus Picrasma. The AChE inhibitory activity and the antimicrobial activity of 1-8 were assessed. In addition, preliminary structure-activity relationships of these β-carboline alkaloids on the AChE inhibitory activity and antimicrobial activity were proposed.

New phthalide derivatives from the Biscogniauxia sp. and their activities

Five new phthalide derivatives, biscogniphthalides A-D (1, 2, 3a/3b, and 4), were isolated from Biscogniauxia sp. (No. 69-8-7-1), along with one related known phthalide (5). Their structures were determined by comprehensive spectroscopic analyses, chemical derivatization, and quantum chemical ECD calculations. In addition, the anti-acetyl cholinesterase, antimicrobial, and anti-α-glucosidase activities of 1-5 were evaluated.

Non-volatile pungent compounds isolated from Zingiber officinale and their mechanisms of action

In this study, an efficient strategy developed by integrating UPLC-Q/TOF-MS, network pharmacology, and molecular simulation, was proposed and applied for rapidly screening bioactive candidates from ginger. A UPLC-Q/TOF MS-guided isolation targeting non-volatile pungent compounds resulted in the isolation and identification of 19 compounds in the rhizome of Zingiber officinale, including six new compounds (1-6). Based on target prediction and Gene Ontology (GO), the primary biological function of compounds was predicted to be associated with cancer and the key target was VEGFR2 (vascular endothelial growth factor receptor 2). Moreover, cytotoxic activity assays demonstrated that the isolated compounds had potential anti-proliferative effects on MDA-MB-231, A549 and HCT116 cells. In particular, compounds 7 and 8 exhibited the highest cytotoxicity against HCT116 compared with the other cell lines, with IC50 values ranging from 4.70 to 7.40 μM. In addition, VEGFR2 inhibition of compounds 7 and 8 was validated based on enzyme activity assays and their interaction mechanisms were illuminated through molecular simulations. These experimental data are consistent with the calculated results, indicating the veracity of the proposed method. In conclusion, the integrated strategy is a quick and efficient way to explore bioactive compounds as well as research the possible targets, providing us with a good possibility of screening new lead compounds from natural sources.

Resistance modulatory and efflux-inhibitory activities of capsaicinoids and capsinoids

Capsaicinoids are reported to have a bunch of promising pharmacological activities, among them antibacterial effects against various strains of bacteria. In this study the effect on efflux pumps of mycobacteria was investigated. The importance of efflux pumps, and the inhibition of these, is rising due to their involvement in antibiotic resistance development. In order to draw structure and activity relationships we tested natural and synthetical capsaicinoids as well as synthetical capsinoids. In an accumulation assay these compounds were evaluated for their ability to accumulate ethidium bromide into mycobacterial cells, a well-known substrate for efflux pumps. Capsaicin and dihydrocapsaicin, the two most abundant capsaicinoids in Capsicum species, proved to be superior efflux pump inhibitors compared to the standard verapamil. A dilution series showed dose dependency of both compounds. The compound class of less pungent capsinoids qualified for further investigation as antibacterials against Mycobacterium smegmatis.

6-Dihydroparadol, a Ginger Constituent, Enhances Cholesterol Efflux from THP-1-Derived Macrophages

SCOPE

Ginger is reported to be used for the prevention and treatment of cardiovascular diseases (CVD). Cholesterol efflux from macrophage foam cells is an important process in reverse cholesterol transport, whose increase may help to prevent or treat CVD. In this study, we investigated the effects of 6-dihydroparadol from ginger on macrophage cholesterol efflux.

METHODS AND RESULTS

We show that 6-dihydroparadol concentration-dependently enhances both apolipoprotein A1- and human plasma-mediated cholesterol efflux from cholesterol-loaded THP-1-derived macrophages using macrophage cholesterol efflux assay. 6-Dihydroparadol increases protein levels of both ATP-binding cassette transporters A1 and G1 (ATP-binding cassette transporter A1 [ABCA1] and ATP-binding cassette transporter G1 [ABCG1]) according to Western blot analysis. The ABCA1 inhibitor probucol completely abolishes 6-dihydroparadol-enhanced cholesterol efflux. Furthermore, increased ABCA1 protein levels in the presence of 6-dihydroparadol were associated with both increased ABCA1 mRNA levels and increased ABCA1 protein stability. Enhanced ABCG1 protein levels were only associated with increased protein stability. Increased ABCA1 protein stability appeared to be the result of a reduced proteasomal degradation of the transporter in the presence of 6-dihydroparadol.

CONCLUSION

We identified 6-dihydroparadol from ginger as a novel promoter of cholesterol efflux from macrophages that increases both ABCA1 and ABCG1 protein abundance. This newly identified bioactivity might contribute to the antiatherogenic effects of ginger.

Analogues of Disulfides from Allium stipitatum Demonstrate Potent Anti-tubercular Activities through Drug Efflux Pump and Biofilm Inhibition

Disulfides from Allium stipitatum, commonly known as Persian shallot, were previously reported to possess antibacterial properties. Analogues of these compounds, produced by S-methylthiolation of appropriate thiols using S-methyl methanethiosulfonate, exhibited antimicrobial activity, with one compound inhibiting the growth of Mycobacterium tuberculosis at 17 µM (4 mg L-1) and other compounds inhibiting Escherichia coli and multi-drug-resistant (MDR) Staphylococcus aureus at concentrations ranging between 32-138 µM (8-32 mg L-1). These compounds also displayed moderate inhibitory effects on Klebsiella and Proteus species. Whole-cell phenotypic bioassays such as the spot-culture growth inhibition assay (SPOTi), drug efflux inhibition, biofilm inhibition and cytotoxicity assays were used to evaluate these compounds. Of particular note was their ability to inhibit mycobacterial drug efflux and biofilm formation, while maintaining a high selectivity towards M. tuberculosis H37Rv. These results suggest that methyl disulfides are novel scaffolds which could lead to the development of new drugs against tuberculosis (TB).

Phenylisotertronic acids from the TCM endophytic fungus Phyllosticta sp

Four new phenylisotertronic acids (1a/1b, 2a, and 3a) were isolated from a TCM endophytic fungal strain Phyllosticta sp. J13-2-12Y obtained from the leaves of Acorus tatarinowii, along with two known ones (2b and 3b). Compounds 1-3 all existed as mixtures of enantiomers, and their corresponding optically pure enantiomers were successfully isolated by chiral HPLC. The structures of isolated compounds were determined by comprehensive spectroscopic analyses and X-ray diffraction. Their absolute configurations were determined by ECD experiments and quantum chemical calculations. In addition, the antimicrobial activities and the cytotoxicities of these three pairs of optically pure enantiomers (1a/1b, 2a/2b, and 3a/3b) had been evaluated.

Phyllomeroterpenoids A-C, Multi-biosynthetic Pathway Derived Meroterpenoids from the TCM Endophytic Fungus Phyllosticta sp. and their Antimicrobial Activities

Phyllomeroterpenoids A−C (1−3), multi-biosynthetic pathway derived meroterpenoids from amino acid/pentose phosphate/terpenoid pathways, were isolated from the TCM endophytic fungus Phyllosticta sp. J13-2-12Y, together with six biosynthetically related compounds (4−9). All structures were determined by extensive spectroscopic analysis, chemical derivatization, and ECD experiments. A plausible biosynthetic pathway of 1−3 was proposed. In addition, the antimicrobial activities of all isolated compounds were evaluated against Staphylococcus aureus 209P (bacterium) and Candida albicans FIM709 (fungus).

Trilobolide-steroid hybrids: Synthesis, cytotoxic and antimycobacterial activity

Sesquiterpene lactone trilobolide is a sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) inhibitor, thus depleting the Ins(1,4,5)P3-sensitive intracellular calcium stores. Here, we describe a synthesis of a series of 6 trilobolide-steroids conjugates (estradiol, pregnene, dehydroepiandrosterone, and testosterone). We found that the newly synthesized Tb-based compounds possess different remarkable biological activities. Cancer cell cytotoxicity and preferential selectivity is represented in our study by a Tb-pregnene derivative. The most cytotoxic clickates of estradiol and pregnene were studied by FACS where impact on cell cycle and RNA synthesis was observed; live-cell microscopy revealed the impact on cell organelle morphology particularly endoplasmic reticulum, mitochondria and nucleus. Further, we have studied the estrogenic and androgenic properties of the clickate molecules using cell-based luciferase assays. Finally, antimycobacterial tests revealed that testosterone and estradiol derivatives potentiated the antimycobacterial activity up to IC50 of 10.6μM.

Pericocins A–D, New Bioactive Compounds from Periconia sp

One new dihydroisocoumarin, pericocin A (1), one new chromone, pericocin B (2), and two new α-pyrone derivatives, pericocins C-D (3–4), together with two known compounds, 3-(2-oxo-2 H-pyran-6-yl)propanoic acid (5) and ( E)-3-(2-oxo-2 H-pyran-6-yl)acrylic acid (6), were isolated from the culture of the endolichenic fungus Periconia sp.. Their structures were elucidated by spectroscopic methods. All these compounds are derived from the polyketone biosynthetic pathway. Compound 1 was obtained as a mixture of enantiomers. The antimicrobial activity of compounds 1–5 was tested against Escherichia coli, Staphylococcus aureus, Aspergillus niger, and Candida albicans. Compounds 1–5 showed moderate antimicrobial activity against A niger and weak activity against C. albicans.

Pericolactines A-C, a New Class of Diterpenoid Alkaloids with Unusual Tetracyclic Skeleton

Fusicoccane diterpenoids usually possess a fused 5-8-5 tricyclic ring system, which are biogenetically generated from geranylgeranyl diphosphate (GGDP). In our report, three novel diterpenoid alkaloids with fusicoccane skeleton, pericolactines A-C (1-3), were isolated from Periconia sp.. Their structures with absolute configurations were determined by spectroscopic analyses and quantum chemical ECD calculation. Pericolactines A-C (1-3) are a new class of diterpenoid alkaloids with an unusual fused 5-5-8-5 tetracyclic ring system, which derive from a geranylgeranyl diphosphate (GGDP) and serine conjugated biosynthesis. They belong to the atypical diterpenoid alkaloids.

Medicinal plants used as excipients in the history in Ghanaian herbal medicine

ETHNOPHARMACOLOGICAL RELEVANCE

The present study was carried out to investigate the traditional use, pharmacology and active compounds of four plants commonly used as excipients in herbal medicine in Ghana.

MATERIALS AND METHODS

A comprehensive literature search was conducted to gain knowledge about the traditional use, pharmacology and active compounds of the four plant excipients. The broth dilution antibacterial assay and the DPPH radical scavenging antioxidant assay were used to evaluate the antibacterial and antioxidant activity of the plants, respectively. Ethanol, warm water and cold water extracts were prepared from the dried seeds/fruits of Aframomum melegueta, Piper guineense, Xylopia aethiopica and Monodora myristica, and tested in the assays.

RESULTS

A. melegueta and P. guineense seemed to act as pharmacoenhancers, since they have been shown to inhibit specific CYP-enzymes. A. melegueta could act as an antioxidant to preserve herbal preparations. None of the plant excipients had antibacterial activity against the bacteria tested in this study. Compounds with an aromatic or pungent smell had been identified in all the plant excipients. An explanation for the use of the plants as excipients could rely on their taste properties.

CONCLUSION

The present study suggests that there may be more than one simple explanation for the use of these four plants as excipients. Plausible explanations have been proven to be: (1) a way to increase the effect of the medicine, (2) a way to make the medicine more palatable or (3) a way to preserve the activity of the medicinal preparation over time.

Gingerols and shogaols: Important nutraceutical principles from ginger

Gingerols are the major pungent compounds present in the rhizomes of ginger (Zingiber officinale Roscoe) and are renowned for their contribution to human health and nutrition. Medicinal properties of ginger, including the alleviation of nausea, arthritis and pain, have been associated with the gingerols. Gingerol analogues are thermally labile and easily undergo dehydration reactions to form the corresponding shogaols, which impart the characteristic pungent taste to dried ginger. Both gingerols and shogaols exhibit a host of biological activities, ranging from anticancer, anti-oxidant, antimicrobial, anti-inflammatory and anti-allergic to various central nervous system activities. Shogaols are important biomarkers used for the quality control of many ginger-containing products, due to their diverse biological activities. In this review, a large body of available knowledge on the biosynthesis, chemical synthesis and pharmacological activities, as well as on the structure-activity relationships of various gingerols and shogaols, have been collated, coherently summarised and discussed. The manuscript highlights convincing evidence indicating that these phenolic compounds could serve as important lead molecules for the development of therapeutic agents to treat various life-threatening human diseases, particularly cancer. Inclusion of ginger or ginger extracts in nutraceutical formulations could provide valuable protection against diabetes, cardiac and hepatic disorders.

Identification and characterization of [6]-shogaol from ginger as inhibitor of vascular smooth muscle cell proliferation

SCOPE

Vascular smooth muscle cell (VSMC) proliferation is involved in the pathogenesis of cardiovascular disease, making the identification of new counteracting agents and their mechanisms of action relevant. Ginger and its constituents have been reported to improve cardiovascular health, but no studies exist addressing a potential interference with VSMC proliferation.

METHODS AND RESULTS

The dichloromethane extract of ginger inhibited VSMC proliferation when monitored by resazurin metabolic conversion (IC50 = 2.5 μg/mL). The examination of major constituents from ginger yielded [6]-shogaol as the most active compound (IC50 = 2.7 μM). In the tested concentration range [6]-shogaol did not exhibit cytotoxicity toward VSMC and did not interfere with endothelial cell proliferation. [6]-shogaol inhibited DNA synthesis and induced accumulation of the VSMC in the G0 /G1 cell-cycle phase accompanied with activation of the nuclear factor-erythroid 2-related factor 2 (Nrf2)/HO-1 pathway. Since [6]-shogaol lost its antiproliferative activity in the presence of the heme oxygenase-1 (HO-1) inhibitor tin protoporphyrin IX, HO-1 induction appears to contribute to the antiproliferative effect.

CONCLUSION

This study demonstrates for the first time inhibitory potential of ginger constituents on VSMC proliferation. The presented data suggest that [6]-shogaol exerts its antiproliferative effect through accumulation of cells in the G0 /G1 cell-cycle phase associated with activation of the Nrf2/HO-1 pathway.

Nodulisporipyrones A-D, new bioactive α-pyrone derivatives from Nodulisporium sp

Four new α-pyrone derivatives, nodulisporipyrones A-D (1-4), were isolated from the extract of an endolichenic fungal strain Nodulisporium sp. (65-12-7-1) that was fermented with rice. The structures of 1-4 were elucidated by extensive spectroscopic analysis, and the absolute configurations were determined by modified Mosher's method and electronic circular dichroism experiments. Their antimicrobial activities against Staphylococcus aureus 209P, Escherichia coli ATCC0111, Aspergillus niger R330, and Candida albicans FIM709 were evaluated using a paper disk diffusion method. Nodulisporipyrones A-D (1-4) are the first α-pyrone derivatives from Nodulisporium fungi.

Antibiotic resistance modulation and modes of action of (-)-α-pinene in Campylobacter jejuni

The aim of the study was to investigate the mode of action of (-)-α-pinene in terms of its modulation of antibiotic resistance in Campylobacter jejuni. Broth microdilution and ethidium bromide accumulation assays were used to evaluate the (-)-α-pinene antimicrobial activity, modulation of antimicrobial resistance, and inhibition of antimicrobial efflux. The target antimicrobial efflux systems were identified using an insertion mutagenesis approach, and C. jejuni adaptation to (-)-α-pinene was evaluated using DNA microarrays. Knock-out mutants of the key up-regulated transcriptional regulators hspR and hrcA were constructed to investigate their roles in C. jejuni adaptation to several stress factors, including osmolytes, and pH, using Biolog phenotypical microarrays. Our data demonstrate that (-)-α-pinene efficiently modulates antibiotic resistance in C. jejuni by decreasing the minimum inhibitory concentrations of ciprofloxacin, erythromycin and triclosan by up to 512-fold. Furthermore, (-)-α-pinene promotes increased expression of cmeABC and another putative antimicrobial efflux gene, Cj1687. The ethidium bromide accumulation was greater in the wild-type strain than in the antimicrobial efflux mutant strains, which indicates that these antimicrobial efflux systems are a target of action of (-)-α-pinene. Additionally, (-)-α-pinene decreases membrane integrity, which suggests that enhanced microbial influx is a secondary mode of action of (-)-α-pinene. Transcriptomic analysis indicated that (-)-α-pinene disrupts multiple metabolic pathways, and particularly those involved in heat-shock responses. Thus, (-)-α-pinene has significant activity in the modulation of antibiotic resistance in C. jejuni, which appears to be mediated by multiple mechanisms that include inhibition of microbial efflux, decreased membrane integrity, and metabolic disruption. These data warrant further studies on (-)-α-pinene to develop its use in the control of antibiotic resistance in Campylobacter.

4,5-seco-Probotryenols A–C, a new type of sesquiterpenoids from Stachybotrys bisbyi

4,5-seco-Probotryenols A–C (1–3), a new type of sesquiterpenoids named seco-probotryane-type sesquiterpenoid, have been obtained from Stachybotrys bisbyi, along with five new botryane skeleton sesquiterpenoids (4, 5, and 8–10).

Pericoterpenoid A, a new bioactive cadinane-type sesquiterpene from Periconia sp

Pericoterpenoid A (1), a new cadinane-type sesquiterpene, was isolated from an endolichenic fungal strain Periconia sp. (No. 19-4-2-1). Its structure was characterized by analyzing the spectroscopic data (IR, MS, 1D- and 2D-NMR). The antimicrobial activity against Escherichia coli, Staphylococcus aureus, Aspergillus niger, and Candida albicans was evaluated. Pericoterpenoid A showed moderate antimicrobial activity against A. niger and weak activity against C. albicans. This is the first report of the presence of cadinane-type sesquiterpene in Periconia sp.

Anti-inflammatory activity of grains of paradise (Aframomum melegueta Schum) extract

The ethanolic extract of grains of paradise (Aframomum melegueta Schum, Zingiberaceae) has been evaluated for inhibitory activity on cyclooxygenase-2 (COX-2) enzyme, in vivo for the anti-inflammatory activity and expression of several pro-inflammatory genes. Bioactivity-guided fractionation showed that the most active COX-2 inhibitory compound in the extract was [6]-paradol. [6]-Shogaol, another compound from the extract, was the most active inhibitory compound in pro-inflammatory gene expression assays. In a rat paw edema model, the whole extract reduced inflammation by 49% at 1000 mg/kg. Major gingerols from the extract [6]-paradol, [6]-gingerol, and [6]-shogaol reduced inflammation by 20, 25 and 38%. respectively when administered individually at a dose of 150 mg/kg. [6]-Shogaol efficacy was at the level of aspirin, used as a positive control. Grains of paradise extract has demonstrated an anti-inflammatory activity, which is in part due to the inhibition of COX-2 enzyme activity and expression of pro-inflammatory genes.

In vitro bactericidal activity of diterpenoids isolated from Aframomum melegueta K.Schum against strains of Escherichia coli, Listeria monocytogenes and Staphylococcus aureus

ETHNOPHARMACOLOGICAL RELEVANCE

The ethnobotanical use of Aframomum melegueta in the treatment of urinary tract and soft tissue infection suggested that the plant has antimicrobial activity.

MATERIALS AND METHODS

To substantiate the folkloric claims, an acetone, 50:50 acetone:methanol and 2:1 chloroform:methanol extracts were tested against Escherichia coli K12; acetone extract and the fractions of acetone extracts were tested against Listeria monocytogenes. Bioassay-guided fractionation was performed on the extract using L. monocytogenes as the test organism to isolate the bioactive compounds which were then tested against all the other organisms.

RESULTS

Four known labdane diterpenes (G3 and G5) were isolated for the first time from the rhizomes of A. melegueta and purified. These were tested against E. coli, L. monocytogenes, methicillin resistant Staphylococus aureus (MRSA) and S. aureus to determine antibacterial activity. The result showed that two compounds G3 and G5 exhibited more potent antibacterial activity compared to the current clinically used antibiotics ampicillin, gentamicin and vancomycin and can be potential antibacterial lead compounds. The structure of the labdane diterpenes were elucidated using nuclear magnetic resonance (NMR) spectroscopy and Mass spectrometry. A possible mode of action of the isolated compound G3 and its potential cytotoxicity towards mammalian cells were also discussed.

CONCLUSION

The results confirmed the presence of antibacterial compounds in the rhizomes of A. melegueta with a favourable toxicity profile which could be further optimized as antibacterial lead compounds.

Acute toxicity, biochemical and haematological study of Aframomum melegueta seed oil in male Wistar albino rats

ETHNOPHARMACOLOGICAL RELEVANCE

Aframomum melegueta is a popular medicinal plant in Nigeria believed to have many agents acting in different ways to bring about human health benefits. This study aimed to determine the acute toxicity, identify some phytochemicals known to be present in this plant and the possible effects on lipid profile, haematological indices and biomarker of prostate and cardiac dysfunction.

MATERIALS AND METHODS

Twenty four Wistar rats (284-326 g) were used in four groups of six animals. Group 1 (control) received normal saline; groups 2, 3 and 4, received intraperitoneal injection of 27.39, 54.77 and 82.16 mg/kg body weight of the extract respectively for 7 days. Haematological and biochemical parameters were measured.

RESULTS

Alkaloids, flavonoids, saponins, tannins, cardiac glycosides, terpenoids and steroids were identified in this plant extract. The LD₅₀ was 273.86 mg/kg body weight. Prostate Specific Antigen (PSA) decreased significantly in group 2. Testosterone increased significantly in all the test groups compared to the control. Cardiac troponin I (0 ng/dl) was recorded for the test groups while the control had 1.69 ± 0.12 ng/dl. Lipid profile results showed increase in HDL and decrease in total cholesterol and LDL-cholesterol. Haemoglobin (Hb) and Red Blood Cells count (RBC) decreased significantly in group 4. White Blood Cells count (WBC), Mean Cell Volume (MCV), Mean Cell Haemoglobin (MCH) and Mean Cell Haemoglobin Concentration (MCHC) did not change significantly.

CONCLUSION

Aframomum melegueta seed oil has the potential of ameliorating benign prostatic hyperplasia (BPH) and cardiac dysfunction as indicated by testosterone, PSA, lipid profile and troponin I levels. The LD₅₀ of 273.86 mg/kg body weight is indicative of mild toxicity. The lower than normal Hb, RBC confirms the possibility of toxicity.

The intrinsic resistome of bacterial pathogens

Intrinsically resistant bacteria have emerged as a relevant health problem in the last years. Those bacterial species, several of them with an environmental origin, present naturally low-level susceptibility to several drugs. It has been proposed that intrinsic resistance is mainly the consequence of the impermeability of cellular envelopes, the activity of multidrug efflux pumps or the lack of appropriate targets for a given family of drugs. However, recently published articles indicate that the characteristic phenotype of susceptibility to antibiotics of a given bacterial species depends on the concerted activity of several elements, what has been named as intrinsic resistome. These determinants comprise not just classical resistance genes. Other elements, several of them involved in basic bacterial metabolic processes, are of relevance for the intrinsic resistance of bacterial pathogens. In the present review we analyze recent publications on the intrinsic resistomes of Escherichia coli and Pseudomonas aeruginosa. We present as well information on the role that global regulators of bacterial metabolism, as Crc from P. aeruginosa, may have on modulating bacterial susceptibility to antibiotics. Finally, we discuss the possibility of searching inhibitors of the intrinsic resistome in the aim of improving the activity of drugs currently in use for clinical practice.