Holly A. Johnson

Bioactive Monoterpenes from Monarda fistulosa (Lamiaceae)

Abstract Bioactivity-guided fractionation of Monarda fistulosa L. (F005), using the brine shrimp lethality test (BST) and crown gall tumor potato disc assay (PD), led to the isolation of the bioactive monoterpenes, thymoquinone (1), and thymol (2). 1, surprisingly, exhibited selective cytotoxicities against certain cell lines. Of over 60 human tumor cell lines evaluated, 1 was very selective for SF-539 (CNS) with an LC50 < 2.51 × 10−2 μg/ml. Other cell lines targeted by 1 were PC-3 (prostate), M-14 (melanoma), OVCAR-5 (ovarian), and MCF-7 (breast). The reduction of 1 to thymohydroquinone (3) resulted in a 1.7 fold decrease in the cytotoxic potency for PC-3. Thymol (2), although not significantly cytotoxic, demonstrated strong pesticidal activity, more potent than rotenone, in the yellow fever mosquito larvae assay (YFM). None of the compounds, 1–3, approached the IC50 value of rotenone in inhibiting oxygen uptake in the rat liver mitochondrial bioassay, suggesting that they must have another mode of action.

SARs of annonaceous acetogenins in rat liver mitochondria

The Annonaceous acetogenins represent a class of compounds with diverse bioactivities, including promising cytotoxicites. These are due, at least in part, to inhibition of complex I in the oxidative phosphorylation pathway in mitochondria. Fourteen Annonaceous acetogenins were tested in a rat liver mitochondrial oxygen uptake assay to probe additional structure-activity relationships. In this subcellular assay, the activity of non-adjacent bis-THF ring acetogenins depends on the distance between the two THF rings; the activity decreases to that of a mono-THF ring acetogenin if the distance is too long. When one THF ring is replaced with a tetrahydropyran ring, the activity remains comparable. The configuration of the THF ring, in mono ring compounds, seems to be more important than stereochemical differences in the rings of adjacent bis-THF ring compounds. Bullatacin, an adjacent bis-THF ring acetogenin, was used as a standard compound in every run to normalize the data.

Quantitative evaluation of Annonaceous acetogenins in monthly samples of paw paw (Asimina triloba) twigs by liquid chromatography/electrospray ionization/tandem mass spectrometry

A quantitative liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was established for the quality control of the Annonaceous acetogenins in the extracts of the paw paw tree, Asimina triloba (L.) Dunal. (Annonaceae). A new calibration method was developed by (a) using the diastereoisomers of analytes present in the same extract as internal standards, and (b) adding five different levels of pure analytes to the extract solutions to construct a calibration curve. These modifications completely eliminate the matrix and instrument variations and, thus, provide high accuracy. As an example, concentrations of the three major and most active Annonaceous acetogenins, bullatacin (1), asimicin (2) and trilobacin (3), were directly evaluated, without any further sample preparation, in crude dichloromethane extracts of twigs collected monthly from a single paw paw tree. The results showed that the contents of 1 and the mixture of 2 and 3 increased significantly in May and June, with 1 at 12.94 and 14.55 ppm, respectively, and the mixture of 2 and 3 at 47.05 and 51.26 ppm, respectively. The quantified contents of these potent acetogenins showed a good correlation with potencies observed in the brine shrimp test (BST), which demonstrated the highest activities with extracts from the May and June samples. These results suggest that May and June are the best time to collect paw paw twigs for maximizing pesticidal and other bioactivities. In addition, the results obtained from both methods, BST and LC/MS/MS, also verify the accuracy of each other, This well-defined LC/MS/MS method can be widely applied in the quantitative analysis of other natural components in crude extracts. Copyright

Annojahnin from Annona jahnii: a possible precursor of mono-tetrahydrofuran acetogenins

A new cytotoxic Annonaceous acetogenin, annojahnin (1), was isolated from the twigs of Annona jahnii (Annonaceae) by bioactivity-directed fractionation using lethality to brine shrimp. Compound 1 represents an unusual type of C-37 Annonaceous acetogenin, lacking either tetrahydrofuran (THF) or epoxide rings, bearing a keto group at C-10, and possessing a double bond located two methylenes away from a vicinal diol. The structure and absolute configuration of 1 were elucidated by 1H and 13C NMR, COSY, and single-relayed COSY and from chemical derivatives. 4-Deoxy-18/21-trans-annomontacin 10-one (4) and 4-deoxy-18/21-cis-annomontacin-10-one (5), two semisynthetic mono-THF acetogenins, were prepared from 1 by reactions that mimic the biogenetic pathways. These acetogenins showed selective cytotoxicities, comparable or superior to adriamycin, among six human solid tumor cell lines. Reduction of the 10-keto of 1, to the racemic 10-OH derivative (3), retained the bioactivities as did the conversion of 1 to 4 and 5.

Annodienin and Jahnonacin: New Bioactive Nontetrahydrofuran Annonaceous Acetogenins from the Twigs of Annona Jahnii

Abstract Annodienin (1) and jahnonacin (2), two new bioactive non-tetrahydrofuran Annonaceous acetogenins, have been isolated from the EtOH extract of the twigs of Annona jahnii Saff., using fractionation directed by brine shrimp lethality. These new compounds are unsaturated acetogenins and have a diol system. Compound 1 bears two double bonds in the aliphatic chain. The structures were elucidated by spectral analyses of the parent compounds and/or simple chemical derivatives, especially by employing 1H-NMR and 2D-NMR experiments. These acetogenins showed selective cytotoxicities, with potencies similar to adriamycin, among six human solid tumor cell lines.