New amide alkaloid from the aerial part of Piper capense L.f. (Piperaceae)

A Lewis Acid-Controlled Enantiodivergent Epoxidation of Aldehydes

Two epoxidation catalysts, one of which consists of two VANOL ligands and an aluminum and the other that consists of two VANOL ligands and a boron, were compared. Both catalysts are highly effective in the catalytic asymmetric epoxidation of a variety of aromatic and aliphatic aldehydes with diazoacetamides, giving high yields and excellent asymmetric inductions. The aluminum catalyst is effective at 0 °C and the boron catalyst at -40 °C. Although both the aluminum and boron catalysts of (R)-VANOL give very high asymmetric inductions (up to 99% ee), they give opposite enantiomers of the epoxide. The mechanism, rate- and enantioselectivity-determining step, and origin of enantiodivergence are evaluated using density functional theory calculations.

1 H and 13 C NMR data, occurrence, biosynthesis, and biological activity of Piper amides

Alkamides are the major and characteristic chemical compounds of the plants belonging to the Piper genus. These compounds are responsible for the flavor of pepper spices and for its broad use in cuisine across many regions of the world. Humans are in contact every day with these substances, which additionally show a broad variety of pharmacological activities, making them an important research target. A large amount of NMR data for these natural products is dispersed throughout literature. Its organization will help those research groups interested in their identification and structural elucidation. This review summarizes the ¹ H and ¹³ C NMR data of 268 Piper amides in a systematic and orderly way, with a discussion on their biological activities, biosynthetic aspects, and NMR analysis of typical and relevant aspects of this information.

Piper Species: A Comprehensive Review on Their Phytochemistry, Biological Activities and Applications

Piper species are aromatic plants used as spices in the kitchen, but their secondary metabolites have also shown biological effects on human health. These plants are rich in essential oils, which can be found in their fruits, seeds, leaves, branches, roots and stems. Some Piper species have simple chemical profiles, while others, such as Piper nigrum, Piper betle, and Piper auritum, contain very diverse suites of secondary metabolites. In traditional medicine, Piper species have been used worldwide to treat several diseases such as urological problems, skin, liver and stomach ailments, for wound healing, and as antipyretic and anti-inflammatory agents. In addition, Piper species could be used as natural antioxidants and antimicrobial agents in food preservation. The phytochemicals and essential oils of Piper species have shown strong antioxidant activity, in comparison with synthetic antioxidants, and demonstrated antibacterial and antifungal activities against human pathogens. Moreover, Piper species possess therapeutic and preventive potential against several chronic disorders. Among the functional properties of Piper plants/extracts/active components the antiproliferative, anti-inflammatory, and neuropharmacological activities of the extracts and extract-derived bioactive constituents are thought to be key effects for the protection against chronic conditions, based on preclinical in vitro and in vivo studies, besides clinical studies. Habitats and cultivation of Piper species are also covered in this review. In this current work, available literature of chemical constituents of the essential oils Piper plants, their use in traditional medicine, their applications as a food preservative, their antiparasitic activities and other important biological activities are reviewed.

The direct and highly diastereoselective synthesis of 3,4-epoxy-2-piperidones. Application to the total synthesis and absolute configurational assignment of 3α,4α-epoxy-5β-pipermethystine

The substrate-controlled asymmetric total synthesis and absolute configurational assignment of biologically active 3α,4α-epoxy-5β-pipermethystine is reported.

Potential of Central, Eastern and Western Africa Medicinal Plants for Cancer Therapy: Spotlight on Resistant Cells and Molecular Targets

Cancer remains a major health hurdle worldwide and has moved from the third leading cause of death in the year 1990 to second place after cardiovascular disease since 2013. Chemotherapy is one of the most widely used treatment modes; however, its efficiency is limited due to the resistance of cancer cells to cytotoxic agents. The present overview deals with the potential of the flora of Central, Eastern and Western African (CEWA) regions as resource for anticancer drug discovery. It also reviews the molecular targets of phytochemicals of these plants such as ABC transporters, namely P-glycoprotein (P-gp), multi drug-resistance-related proteins (MRPs), breast cancer resistance protein (BCRP, ABCG2) as well as the epidermal growth factor receptor (EGFR/ErbB-1/HER1), human tumor suppressor protein p53, caspases, mitochondria, angiogenesis, and components of MAP kinase signaling pathways. Plants with the ability to preferentially kills resistant cancer cells were also reported. Data compiled in the present document were retrieved from scientific websites such as PubMed, Scopus, Sciencedirect, Web-of-Science, and Scholar Google. In summary, plant extracts from CEWA and isolated compounds thereof exert cytotoxic effects by several modes of action including caspases activation, alteration of mitochondrial membrane potential (MMP), induction of reactive oxygen species (ROS) in cancer cells and inhibition of angiogenesis. Ten strongest cytotoxic plants from CEWA recorded following in vitro screening assays are: Beilschmiedia acuta Kosterm, Echinops giganteus var. lelyi (C. D. Adams) A. Rich., Erythrina sigmoidea Hua (Fabaceae), Imperata cylindrical Beauv. var. koenigii Durand et Schinz, Nauclea pobeguinii (Pobég. ex Pellegr.) Merr. ex E.M.A., Piper capense L.f., Polyscias fulva (Hiern) Harms., Uapaca togoensis Pax., Vepris soyauxii Engl. and Xylopia aethiopica (Dunal) A. Rich. Prominent antiproliferative compounds include: isoquinoline alkaloid isotetrandrine (51), two benzophenones: guttiferone E (26) and isoxanthochymol (30), the isoflavonoid 6α-hydroxyphaseollidin (9), the naphthyl butenone guieranone A (25), two naphthoquinones: 2-acetylfuro-1,4-naphthoquinone (4) and plumbagin (37) and xanthone V1 (46). However, only few research activities in the African continent focus on cytotoxic drug discovery from botanicals. The present review is expected to stimulate further scientific efforts to better valorize the African flora.

Sensory active piperine analogues from Macropiper excelsum and their effects on intestinal nutrient uptake in Caco-2 cells

The phytochemical profile of Macropiper excelsum (G.Forst.) Miq. subsp. excelsum (Piperaceae), a shrub which is widespread in New Zealand, was investigated by LC-MS-guided isolation and characterization via HR-ESI-TOF-MS and NMR spectroscopy. The isolated compounds were sensorily evaluated to identify their contribution to the overall taste of the crude extract with sweet, bitter, herbal and trigeminal impressions. Besides the known non-volatile Macropiper compounds, the lignans (+)-diayangambin and (+)-excelsin, four further excelsin isomers, (+)-diasesartemin, (+)-sesartemin, (+)-episesartemin A and B were newly characterized. Moreover, piperine and a number of piperine analogues as well as trans-pellitorine and two homologues, kalecide and (2E,4E)-tetradecadienoic acid N-isobutyl amide were identified in M. excelsum, some of them for the first time. Methyl(2E,4E)-7-(1,3-benzodioxol-5-yl)hepta-2,4-dienoate was identified and characterized for the first time in nature. Sensory analysis of the pure amides indicated that they contributed to the known chemesthetic effects of Macropiper leaves and fruits. Since the pungent piperine has been shown to affect glucose and fatty acid metabolism in vivo in previous studies, piperine itself and four of the isolated compounds, piperdardine, chingchengenamide A, dihydropiperlonguminine, and methyl(2E,4E)-7-(1,3-benzodioxol-5-yl)hepta-2,4-dienoate, were investigated regarding their effects on glucose and fatty acid uptake by enterocyte-like Caco-2 cells, in concentrations ranging from 0.1 to 100 μM. Piperdardine showed the most pronounced effect, with glucose uptake increased by 83 ± 18% at 100 μM compared to non-treated control cells. An amide group seems to be advantageous for glucose uptake stimulation, but not necessarily for fatty acid uptake-stimulating effects of piperine-related compounds.

Synthesis of the Enantiomers of Tedanalactam and the First Total Synthesis and Configurational Assignment of (+)-Piplaroxide

Highlighting the recently established methodology for the direct synthesis of glycidic amides from tertiary allyl amines, the synthesis of the enantiomers of tedanalactam were completed in two steps from the corresponding chiral dihydropiperidine. Additionally, the (+)- and (-)-enantiomers of piplaroxide were obtained from their respective tedanalactam precursor, and the absolute configuration of the naturally occurring (+)-piplaroxide was determined. The present approach represents not only the shortest synthesis of (-)-tedanalactam but also the first total synthesis of (+)-piplaroxide, a repellent against the leafcutter ant Atta cephalotes.

Bioactivity-guided isolation of laevicarpin, an antitrypanosomal and anticryptococcal lactam from Piper laevicarpu (Piperaceae)

Crude CH2Cl2 extract from leaves of Piper laevicarpu (Piperaceae) displayed antitrypanosomal activity against trypomastigote forms of Trypanosoma cruzi (Y strain) and antimicrobial potential against Cryptococcus gattii (strain-type WM 178). Bioactivity-guided fractionation of crude extract afforded one new natural bioactive lactam derivative, named laevicarpin. The structure of isolated compound, which displayed a very rare ring system, was elucidated based on NMR, IR and MS spectral analysis. Using MTT assay, the trypomastigotes of T. cruzi demonstrated susceptibility to laevicarpin displaying IC50 value of 14.7μg/mL (49.6μM), about 10-fold more potent than the standard drug benznidazole. The mammalian cytotoxicity of laevicarpin was verified against murine fibroblasts (NCTC cells) and demonstrated a CC50 value of 100.3μg/mL (337.7μM-SI=7). When tested against Cryptococcus gattii, laevicarpin showed an IC50 value of 2.3μg/mL (7.9μM) and a MIC value of 7.4μg/mL (25μM). Based in the obtained results, laevicarpin could be used as a scaffold for future drug design studies against the Chagas disease and anti-cryptococosis agents.

Protective Effect of Piper aduncum Capsule on DMBA-induced Breast Cancer in Rats

The possible protective effect of Piper aduncum capsule on DMBA (dimethylbenz[α]anthracene)-induced breast cancer in rats was assessed by monitoring the tumor and lung metastases incidence and recording hematological and biochemical parameters and frequency of micronuclei. Mammary carcinogenesis was induced in 36 female Holtzman rats by providing a single subcutaneous injection of DMBA. Oral administration of P. aduncum capsule lowered adenocarcinoma and lymph node metastases incidence. Pulmonary metastasis was significantly lowered (P < 0.05). Hematological indicators showed that the triglyceride level was significantly lowered (P < 0.01) and high-density lipoprotein (HDL) level was significantly increased (P < 0.01). Also, P. aduncum capsule significantly lowered the C reactive protein (CRP) level (P < 0.01) and malondialdehyde level (P < 0.05). There was a significant decrease in the frequency of DMBA-induced micronucleated polychromatic erythrocyte (P < 0.01). Considering the antitumorigenic, hypolipidemic, anti-inflammatory, antioxidant, and antigenotoxic properties of P. aduncum capsule, we conclude that it has a protective effect on DMBA-induced breast cancer in rats.

African flora has the potential to fight multidrug resistance of cancer

Background. Continuous efforts from scientists of diverse fields are necessary not only to better understand the mechanism by which multidrug-resistant (MDR) cancer cells occur, but also to boost the discovery of new cytotoxic compounds to fight MDR phenotypes. Objectives. The present review reports on the contribution of African flora in the discovery of potential cytotoxic phytochemicals against MDR cancer cells. Methodology. Scientific databases such as PubMed, ScienceDirect, Scopus, Google Scholar, and Web of Knowledge were used to retrieve publications related to African plants, isolated compounds, and drug resistant cancer cells. The data were analyzed to highlight cytotoxicity and the modes of actions of extracts and compounds of the most prominent African plants. Also, thresholds and cutoff points for the cytotoxicity and modes of action of phytochemicals have been provided. Results. Most published data related to the antiproliferative potential of African medicinal plants were from Cameroon, Egypt, Nigeria, or Madagascar. The cytotoxicity of phenolic compounds isolated in African plants was generally much better documented than that of terpenoids and alkaloids. Conclusion. African flora represents an enormous resource for novel cytotoxic compounds. To unravel the full potential, efforts should be strengthened throughout the continent, to meet the challenge of a successful fight against MDR cancers.

Antioxidant, Antiproliferative and Antimicrobial Activities of the Volatile Oil from the Wild Pepper Piper capense Used in Cameroon as a Culinary Spice

Wild pepper (Piper capense L.f., Piperaceae) is a spice traditionally used in western Cameroon to make soups called ‘ Nkui’ and ‘ Nah poh’. In the present work, the essential oil hydrodistilled from fruits was analyzed by GC-FID and GC-MS, and for in vitro biological activities, namely cytotoxic, antioxidant and antimicrobial, by MTT, DPPH, ABTS and agar disc diffusion methods. The oil composition was dominated by monoterpene hydrocarbons (56.5%) responsible for the pepper odor, such as β-pinene (33.2%), sabinene (10.0%) and α-pinene (8.9%). The oil induced a concentration-dependent inhibitory effect on human tumor cells MDA-MB 231 (breast adenocarcinoma), A375 (malignant melanoma) and HCT116 (colon carcinoma), showing IC50 values of 26.3, 76.0 and 22.7 μg/ml, respectively. The oil showed total antioxidant activity with a Trolox equivalent antioxidant concentration (TEAC) value of 140 μmol/g. The essential oil of P. capense proved to be an effective scavenger of the ABTS+ radical, with an activity only about 30 times lower than that of Trolox. Moderate activity was observed against the Gram-positive species Staphylococcos aureus and Enterococcus faecalis, and the yeast Candida albicans. The notable inhibition of some human tumor cells is worthy of further investigation to discover the possible mechanisms of action responsible for the observed cytotoxic effect of this essential oil.

Antibacterial activity of selected Cameroonian dietary spices ethno-medically used against strains of Mycobacterium tuberculosis

ETHNOPHARMACOLOGICAL RELEVANCE

Tuberculosis (TB) is considered as a re-emerging disease and one of the most important public health problems worldwide. The use or (in most cases) misuse of existint anti-tuberculosis drugs over the years has led to an increasing prevalence of resistant strains, establishing an urgent need to search for new effective agents. Spices are largely used ethno-medically across Africa.

AIM OF THE STUDY

The present study aimed to evaluate the in vitro antimycobacterial activities of a total of 20 methanol crude extracts prepared from 20 Cameroonian dietary spices for their ability to inhibit the growth of or kill Mycobacterium tuberculosis strains H(37)Rv (ATCC 27294) and H(37)Ra (ATCC 25177).

MATERIALS AND METHODS

The antituberculosis screening was performed using the Microplate Alamar Blue Assay (MABA) method to determine the minimum inhibitory concentration (MIC) and the minimum mycobactericidal concentration (MBC).

RESULTS

Fifteen (15) plant extracts out of 20 showed varied levels of antimycobacterial activity against the strains M. tuberculosis H(37)Rv and H(37)Ra, with MICs in the range of 2.048-0.016 mg/ml. The extract of Echinops giganteus exhibited the most significant activity with a MIC value of 32 μg/ml and 16 μg/ml, respectively against H(37)Ra and H(37)Rv. To the best of our knowledge, the antimycobacterial activity of the tested spices has not been reported before and therefore our results can be evaluated as the first report about the antimycobacterial properties.

CONCLUSIONS

The results of this study suggest that Echinops giganteus and Piper guineense could be important sources of bactericidal compounds against M. tuberculosis and could probably be promising candidates that can be further investigated.

Cytotoxicity of some Cameroonian spices and selected medicinal plant extracts

ETHNOPHARMACOLOGICAL RELEVANCE

Several medicinal plants and spices are used traditionally to treat cancers in Cameroon.

AIM

Methanol extracts from thirty-four spices and plants, with related ethnobotanical use were investigated for their in vitro cytotoxicity on the human pancreatic cancer cell line MiaPaCa-2, leukemia CCRF-CEM cells and their multidrug resistant (MDR) subline CEM/ADR5000, and the normal human umbilical vein endothelial cells (HUVECs). In addition the anti-angiogenic properties of the most active extracts were investigated.

MATERIAL AND METHODS

The MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assay was used for cytotoxic studies and the CAM-assay (chicken-chorioallantoic-membrane-assay) for anti-angiogenesis test.

RESULTS

The results of the cytotoxicity tests indicated that, when tested at 20 μg/ml, extracts from Xylopia aethiopica, Echinops giganteus, Imperata cylindrica, Dorstenia psilirus and Piper capense were able to inhibit more that 50% the proliferation of the three tested cancer cells (MiaPaCa-2, CEM/ADR5000 CCRF-CEM). The lowest IC(50) values of 6.86 μg/ml on MiaPaCa-2 and 3.91 μg/ml on CCRF-CEM cells were obtained with X. aethiopica, while the corresponding value of 6.56 μg/ml was obtained with P. capense on CEM/ADR5000 cells. Against leukemia cells, no cross-resistance was observed with I. cylindrica, P. capense and Zinziber officinalis. Extracts from D. psilirus and E. giganteus were able to inhibit angiogenesis by more than 50% in quail embryo.

CONCLUSION

The overall results of the present study provide supportive data on the use of some Cameroonian plants for cancer treatment.