Antiplasmodial and Antileishmanial Activities of a New Limonoid and Other Constituents from the Stem Bark of Khaya senegalensis.

Plasmodium falciparum and Leishmania sp. resistance to antiparasitic drugs has become a major concern in malaria and leishmaniasis control. These diseases are public health problems with significant socioeconomic impacts, and mostly affect disadvantaged populations living in remote tropical areas. This challenge emphasizes the need to search for new chemical scaffolds that preferably possess novel modes of action to contribute to antimalarial and antileishmanial research programs. This study aimed to investigate the antimalarial and antileishmanial properties of a methanol extract (KS-MeOH) of the stem bark of the Cameroonian medicinal plant Khaya senegalensis and its isolated compounds. The purification of KS-MeOH led to the isolation of a new ordered limonoid derivative, 21ß-hydroxybourjotinolone A (1a), together with 15 known compounds (1bc-14) using a repeated column chromatography. Compound 1a was obtained in an epimeric mixture of 21α-melianodiol (1b) and 21ß-melianodiol (1c). Structural characterization of the isolated compounds was achieved with HRMS, and 1D- and 2D-NMR analyses. The extracts and compounds were screened using pre-established in vitro methods against synchronized ring stage cultures of the multidrug-resistant Dd2 and chloroquine-sensitive/sulfadoxine-resistant 3D7 strains of Plasmodium falciparum and the promastigote form of Leishmania donovani (1S(MHOM/SD/62/1S). In addition, the samples were tested for cytotoxicity against RAW 264.7 macrophages. Positive controls consisted of artemisinin and chloroquine for P. falciparum, amphotericin B for L. donovani, and podophyllotoxin for cytotoxicity against RAW 264.7 cells. The extract and fractions exhibited moderate to potent antileishmanial activity with 50% inhibitory concentrations (IC50) ranging from 5.99 ± 0.77 to 2.68 ± 0.42 µg/mL, while compounds displayed IC50 values ranging from 81.73 ± 0.12 to 6.43 ± 0.06 µg/mL. They were weakly active against the chloroquine-sensitive/sulfadoxine-resistant Pf3D7 strain but highly potent toward the multidrug-resistant PfDd2 (extracts, IC50 2.50 ± 0.12 to 4.78 ± 0.36 µg/mL; compounds IC50 2.93 ± 0.02 to 50.97 ± 0.37 µg/mL) with selectivity indices greater than 10 (SIDd2 > 10) for the extract and fractions and most of the derived compounds. Of note, the limonoid mixture [21ß-hydroxylbourjotinolone A (1a) + 21α-melianodiol (1b) + 21ß-melianodiol (1c)] exhibited moderate activity against P. falciparum and L. donovani. This novel antiplasmodial and antileishmanial chemical scaffold qualifies as a promising starting point for further medicinal chemistry-driven development of a dually active agent against two major infectious diseases affecting humans in Africa.

Synthetic Origin of Tramadol in the Environment.

The presence of tramadol in roots of Sarcocephalus latifolius trees in Northern Cameroon was recently attributed to point contamination with the synthetic compound. The synthetic origin of tramadol in the environment has now been unambiguously confirmed. Tramadol samples isolated from tramadol pills bought at a street market in downtown Maroua and highly contaminated soil at Houdouvou were analyzed by high-precision (14)C measurements by accelerator mass spectrometry ((14)C AMS): Tramadol from the pills did not contain any radiocarbon, thus indicating that it had been synthesized from (14)C-free petroleum-derived precursors. Crucially, tramadol isolated from the soil was also radiocarbon-free. As all biosynthetic plant compounds must contain radiocarbon levels close to that of the contemporary environment, these results thus confirm that tramadol isolated from the soil cannot be plant-derived. Analyses of S. latifolius seeds, in vitro grown plants, plants from different origins, and stable-isotope labeling experiments further confirmed that synthetic tramadol contaminates the environment.

Tramadol--a true natural product?

We have independently investigated the source of tramadol, a synthetic analgesic largely used for treating moderate to severe pain in humans, recently found in the roots of the Cameroonian medicinal plant, Nauclea latifolia. We found tramadol and its three major mammalian metabolites (O-desmethyltramadol, N-desmethyltramadol, and 4-hydroxycyclohexyltramadol) in the roots of N. latifolia and five other plant species, and also in soil and local water bodies only in the Far North region of Cameroon. The off-label administration of tramadol to cattle in this region leads to cross-contamination of the soil and water through feces and urine containing parent tramadol as well as tramadol metabolites produced in the animals. These compounds can then be absorbed by the plant roots and also leached into the local water supplies. The presence of tramadol in roots is, thus, due to an anthropogenic contamination with the synthetic compound.

Antimicrobial and antioxidant activity of kaempferol rhamnoside derivatives from Bryophyllum pinnatum.

BACKGROUND: Bryophyllum pinnatum (Lank.) Oken (Crassulaceae) is a perennial succulent herb widely used in traditional medicine to treat many ailments. Its wide range of uses in folk medicine justifies its being called "life plant" or "resurrection plant", prompting researchers' interest. We describe here the isolation and structure elucidation of antimicrobial and/or antioxidant components from the EtOAc extract of B. pinnatum. RESULTS: The methanol extract displayed both antimicrobial activities with minimum inhibitory concentration (MIC) values ranging from 32 to 512 µg/ml and antioxidant property with an IC50 value of 52.48 µg/ml. Its partition enhanced the antimicrobial activity in EtOAc extract (MIC = 16-128 µg/ml) and reduced it in hexane extract (MIC = 256-1024 µg/ml). In addition, this process reduced the antioxidant activity in EtOAc and hexane extracts with IC50 values of 78.11 and 90.04 µg/ml respectively. Fractionation of EtOAc extract gave seven kaempferol rhamnosides, including; kaempferitrin (1), kaempferol 3-O-α-L-(2-acetyl)rhamnopyranoside-7-O-α-L-rhamnopyranoside (2), kaempferol 3-O-α-L-(3-acetyl)rhamnopyranoside-7-O-α-L-rhamnopyranoside (3), kaempferol 3-O-α-L-(4-acetyl)rhamnopyranoside-7-O-α-L-rhamnopyranoside (4), kaempferol 3-O-α-D- glucopyranoside-7-O-α-L-rhamnopyranoside (5), afzelin (6) and α-rhamnoisorobin (7). All these compounds, except 6 were isolated from this plant for the first time. Compound 7 was the most active, with MIC values ranging from 1 to 2 µg/ml and its antioxidant activity (IC50 = 0.71 µg/ml) was higher than that of the reference drug (IC50 = 0.96 µg/ml). CONCLUSION: These findings demonstrate that Bryophyllum pinnatum and some of its isolated compounds have interesting antimicrobial and antioxidant properties, and therefore confirming the traditional use of B. pinnatum in the treatment of infectious and free radical damages.

Antimicrobial principle from Aframomum longifolius.

Antimicrobial activity-directed fractionation of the seeds of Aframomum longifolius (Zingiberaceae) afforded two new labdane-type diterpenoids, 15-hydroxy-15-methoxylabda-8(17), 12( E)-dien-16-al (aframolin A) ( 1) and 8beta(17)-epoxy-15,15-dimethoxylabd-12( E)-en-16-al (aframolin B) ( 2), together with the known diterpenes labda-8(17),12( E)-diene-15,16-dial ( 3) and aframodial ( 4). Their structures were determined by spectroscopic methods. Compound 4 showed significant antimicrobial activity against Cryptococcus neoformans, Staphylococcus aureus and methicillin-resistant S. aureus (MRS) while 1, 2 and 3 were found to be inactive.

Novel antimicrobial diterpenoids from Turraeanthus africanus.

The dichloromethane-methanol (1/1) extract of the stem bark of Turraeanthus africanus (Meliaceae) showed remarkable antimicrobial activity against Cryptococcus neoformans, Staphylococcus aureus and methicillin-resistant S. aureus. Phytochemical investigation of this extract afforded six new diterpenoid derivatives, (+)-16-acetoxy-12,15-epoxylabda-8(17),12,14-triene ( 3), [16( E),12 S,15 R]-16-acetoxy-12,15-epoxy-15-isopropoxy- ent-labda-8(17),13(16)-diene (turraeanin A, 4), [16( E),12 R,15 S]-16-acetoxy-12,15-epoxy-15-isopropoxy- ent-labda-8(17),13(16)-diene (turraeanin B, 5), [16( E),12 S,15 R]-16-acetoxy-12,15-epoxy-15-methoxy- ent-labda-8(17),13(16)-diene (turraeanin C, 6), [16( E),12 R,15 S]-16-acetoxy-12,15-epoxy-15-methoxy- ent-labda-8(17),13(16)-diene (turraeanin D, 7) and (12 S,13 S,15 R)-12,15-epoxy-15-methoxy- ent-labd-8(17)-en-16-al (turraeanin E, 9) together with the known compounds, 15,16-epoxy- ent-labda-8(17),13(16),14-triene ( 1), (+)-pumiloxide ( 2), ent-labda-8(17),12 ( E)-diene-15,16-dial ( 8) and 16-acetoxy-12( R),15-epoxy-15beta-hydroxylabda-8(17),13 (16)-diene ( 10). Compound 10 was obtained as its acetoxy derivative ( 10a) and compound 11 was the product of hydrolysis of 6. Antimicrobial activity of the isolates was assayed and compounds 8, 9, 10a and 11 exhibited significant activities.