Clausena anisata and Dysphania ambrosioides essential oils: from ethno-medicine to modern uses as effective insecticides

Dysphania ambrosioides (L.) Mosyakin & Clemants (Amaranthaceae) and Clausena anisata (Willd.) Hook. f. ex Benth. (Rutaceae) are two aromatic species traditionally used in Cameroon to repel and kill insects. The present work was carried out to substantiate this traditional use and to evaluate the possible incorporation in commercial botanical insecticides of their essential oils (EOs). The EOs were distilled from leaves of C. anisata and aerial parts of D. ambrosioides and analyzed by gas chromatography-mass spectrometry (GC-MS). The insecticidal activity of both EOs was investigated against the filariasis vector, Culex quinquefasciatus, and the housefly, Musca domestica. As possible mode of action, the inhibition of acetylcholinesterase (AChE) by the two EOs was investigated as well. The D. ambrosioides EO was characterized by the monoterpene peroxide ascaridole (61.4%) and the aromatic p-cymene (29.0%), whereas the C. anisata EO was dominated by the phenylpropanoids (E)-anethole (64.6%) and (E)-methyl isoeugenol (16.1%). The C. anisata EO proved to be very toxic to third instar larvae of C. quinquefasciatus showing LC50 of 29.3 μl/l, whereas D. ambrosioides EO was more toxic to adults of M. domestica showing a LD50 of 51.7 μg/adult. The mixture of both EOs showed a significant synergistic effect against mosquito larvae with LC50 estimated as 19.3 μl/l, whereas this phenomenon was not observed upon application to M. domestica adults (LD50 = 75.9 μg/adult). Of the two EOs, the D. ambrosioides one provided a good inhibition of AChE (IC50 = 77 μg/ml), whereas C. anisata oil was not effective. These findings provide new evidences supporting the ethno-botanical use of these two Cameroonian plants, and their possible application even in synergistic binary blends, to develop new eco-friendly, safe and effective herbal insecticides

Anticandidal activity of the volatile oil from the aphrodisiac Cameroonian spice Mondia whitei (Hook. F.) Skeels

M. whitei is widely distributed in moist to wet areas of tropical Africa and used in several countries by traditional healers since ancient time. Previously, some biological activities were recognized for methanolic extracts of M. whitei such as antibacterial, antifungal and antioxidant. The ethanolic extracts of M. whitei displayed cytoxic effects on breast cancer cell lines and less toxicity toward the non-tumor cell line. In this work we investigated the chemical composition, antimicrobial activity, antioxidant capacity and the effect on the growth of some human tumour cell lines of the essential oil form the plant roots. Dry roots were grounded and hydrodistilled in clevenger-type apparatus for 6 hours. Volatile components were separated by GC and analysed by MS. The major component was the MBE accounting for 79.6% of the oil, followed by benzyl isothiocyanate, BITC (12.4%). The antioxidant activity of from M. whitei essential oil was measured by using different radical scavenging methods such as DPPH, ABTS assay and ferric reducing antioxidant power (FRAP assay). There was antioxidant activity that could be mainly attributed to the presence of MBE. The cytotoxicity was tested on cancer cell lines using the MTT assay. Results indicated that the essential oil was toxic to all cancer cell lines. The IC50 ranged from 5.5 to 6.77 μg/mL (28.8 to 35.42 μM for MBE; 4.6 to 5.6 μM for BITC), values close to the IC50 of cisplatin, used as the positive control. Antimicrobial activity of the essential oil was assessed by disc diffusion and microdilution methods. The essential oil had a wide spectrum of activity. All the species, namely Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Candida albicans were inhibited. The present study provides additional data on the root bark essential oil of M. whitei that support the possible utilization and development of this as an antimicrobial and antioxidant agent. Equally important, the essential oil could be an alternative resource for preparing 2-hydroxy-4-methoxybenzaldehyde an important aroma and flavoring agent that could be used in production of soft drinks, beer and bakery products

Traditional herbal remedies and dietary spices from Cameroon as novel sources of larvicides against filariasis mosquitoes?

In Cameroon, many dietary spices are used by traditional healers to cure several diseases such as cancer and microbial infections. Aframomum daniellii, Dichrostachys cinerea and Echinops giganteus are Cameroonian spices widely used as flavourings and as food additives. Moreover, they are traditionally herbal remedies employed to treat several diseases, as well as to control populations of insect pests. In this research, we analysed the chemical composition of A. daniellii, D. cinerea and E. giganteus essential oils and we evaluated their larvicidal potential against larvae of the filariasis and West Nile virus vector Culex quinquefasciatus. The essential oils were obtained from different plant parts by hydrodistillation and their composition was analysed by GCMS. The three spices exhibited different volatile chemical profiles, being characterized by 1,8-cineole, sabinene and β-pinene (A. daniellii), geraniol and terpinen-4-ol (D. cinerea), and silphiperfol-6-ene and presilphiperfolan-8-ol (E. giganteus). Results showed that the highest larvicidal toxicity on Cx. quinquefasciatus was exerted by D. cinerea essential oil (LC50 = 39.1 μL L−1), followed by A. daniellii (pericarp essential oil: LC50 = 65.5 μL L−1; leaves: LC50 = 65.5μL L−1; seeds: LC50 = 106.5μL L−1) and E. giganteus (LC50 = 227.4 μL L−1). Overall, the chance to use the D. cinerea essential oil against Cx. quinquefasciatus young instars seems promising, since it is effective at moderate doses and could be an advantageous alternative to build newer mosquito control tools

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