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Biomedical subjects

J L McLaughlin

Publications and source records attributed to J L McLaughlin.

At least 109 records · Page 6Linked to original sources
PubMed1992

Evaluation of various parts of the paw paw tree, Asimina triloba (Annonaceae), as commercial sources of the pesticidal annonaceous acetogenins.

Various plant parts of the paw paw tree (Asimina triloba Dunal, Annonaceae) were extracted and partitioned to concentrate the mixture of acetogenins into a standardized pesticidal extract (F005). A bioassay with brine shrimp larvae (Artemia salina Leach) was used to determine the relative potencies of the various extracts. The small twigs (0-0.5 cm diameter) yielded the most potent extract (LC50 = 0.04 ppm); the stem wood (LC50 = 4.9 ppm) and leaves (LC50 = 53.7 ppm) yielded the poorest activities. The unripe fruits, seeds, root wood, root bark, and stem bark were notably potent and, generally, yielded > 2% of their dry weight as F005. The smaller diameter stems were more potent than the larger stems. We conclude that, by pollarding the trees, the entire twigs and small branches of paw paw could be processed to produce a potent acetogenin mixture; this biomass could be made available in quantities needed for commercialization of the pesticidal product and could be renewable through regrowth from the parent trunk and larger branches.

Animals↗
PubMed1991

Cytotoxic clerodane diterpenes from Polyalthia longifolia.

Bioassay-directed chemical investigation of the stem bark of Polyalthia longifolia Thw. (Annonaceae) has led to a novel clerodane diterpene, 16-oxo-cleroda-3, 13(14)Z-dien-15-oic acid, which was named polyalthialdoic acid (3). The bioassays also led to the previously known related diterpenes, kolavenic acid (2) which has not been reported as a constituent of this plant, and 16 alpha-hydroxy-cleroda-3,13(14)Z-dien-15,16-olide (1) which is previously known to be in this plant. These structures were identified by chemical and spectroscopic methods. All three compounds (1-3) were significantly bioactive in the brine shrimp bioassay; they strongly inhibited the growth of crown gall tumors on potato discs; and they were cytotoxic in three human tumor cell lines. These activities suggest potential antitumor applications. Compound 3 was the most active (ED50 values ca. 6 x 10(-1) micrograms/ml in the human tumor cell culture systems).

Antineoplastic Agents, Phytogenic↗
PubMed1990

Gigantecin: a novel antimitotic and cytotoxic acetogenin, with nonadjacent tetrahydrofuran rings, from Goniothalamus giganteus (Annonaceae).

Gigantecin (I), a novel tetrahydroxy-di-tetrahydrofuran fatty acid gamma-lactone (acetogenin), was isolated from an ethanolic extract of the stem bark of Goniothalamus giganteus Hook. f., Thomas (Annonaceae), by means of activity-directed fractionation (brine shrimp lethality test). This new compound is extremely cytotoxic to human tumor cells, inhibits crown gall tumors on potato discs, and is active in an assay designed to detect antimitotic agents (9 ASK).

Animals↗
PubMed1990

16 alpha-hydroxy-(-)-kauranoic acid: a selectively cytotoxic diterpene from Annona bullata.

Using brine shrimp lethality to direct fractionation, extracts of the bark of Annona bullata Rich. (Annonaceae) have yielded 16 alpha-hydroxy-(-)-kauranoic acid as a bioactive plant constituent. This previously known diterpene showed significant (ED50 8.25 x 10(-2) micrograms/ml) and selective cytotoxicity against A-549 (lung) cells in our panel of human tumor cells.

Acetylation↗
PubMed1989

Piceatannol (3,4,3',5'-tetrahydroxy-trans-stilbene) is a naturally occurring protein-tyrosine kinase inhibitor.

Piceatannol (3,4,3'5'-tetrahydroxy-trans-stilbene), a plant secondary natural product that had previously been identified as an antileukemic principle, has been shown to be an inhibitor of protein-tyrosine kinase activity. Piceatannol inhibits the purified thymocyte protein-tyrosine kinase, p40, by competing for the peptide or protein substrate binding site (Ki = 15 microM). Piceatannol also inhibits the activity of the p56lck protein-tyrosine kinase measured either in LSTRA cell membranes or in intact cells. In contrast, piceatannol does not inhibit the activity of the cAMP-dependent protein kinase.

Amino Acid Sequence↗
PubMed1988

Goniothalamicin and annonacin: bioactive acetogenins from Goniothalamus giganteus (Annonaceae).

Using brine shrimp lethality for activity-directed fractionation, goniothalamicin (I), a new tetrahydroxy-mono-tetrahydrofuran fatty acid gamma-lactone (acetogenin), has been isolated from ethanolic extracts of the stem bark of Goniothalamus giganteus Hook. f., Thomas (Annonaceae). This novel compound was found to be cytotoxic and insecticidal and inhibited the formation of crown gall tumors on potato discs. Annonacin (II), the only other reported mono-tetrahydrofuran acetogenin, was also isolated; the previously reported 9ASK (astrocytoma reversal) activity of II was confirmed, and II is now also found to be weakly active against 3PS murine leukemia.

Animals↗
PubMed1988

Isolation, via activity-directed fractionation, of mercaptobenzothiazole and dibenzothiazyl disulfide as 2 allergens responsible for tennis shoe dermatitis.

Although contact dermatitis from shoes is common, the causative allergen is frequently not known. Reliance cannot be placed on standard screening trays because such testing can be negative when testing to shoe materials is positive. Furthermore, the relevance of positive screening tests is almost never proven by extracting that allergen from the patient's shoes. We present a case of insole dermatitis to tennis shoes in which we directly isolated the causative allergens by step-by-step patch-test monitoring of active fractions. Chromatographic separation of the active fractions led to the isolation of 2 allergens, mercaptobenzothiazole (Captax) (MBT) and its dimer, dibenzothiazyl disulfide (Altax) (DBTD). Patch tests to DBTD were noticeably more potent than those to MBT. In what might be considered an obvious case of contact sensitivity to MBT, the actual allergen is DBTD. Using this method, unknown shoe allergens can be isolated, identified, and added to the shoe test tray of potential allergens.

Benzothiazoles↗
PubMed1983

(-)-alpha-Isosparteine from Lupinus argenteus var. stenophyllus.

Combined GLC-mass spectrometry revealed that an unidentified sparteine isomer was the major component of an alkaloid extract of the aboveground portions of Lupinus argenteus Pursh. var. stenophyllus (Rydb.) Davis (Leguminosae). After isolation, this alkaloid was characterized as the least common of the known sparteine isomers, (-)-alpha-isosparteine. A preliminary pharmacological study showed (-)-alpha-isosparteine to have a more rapid onset and a shorter duration of action when compared with (-)-sparteine on rat myocardium.

Chemical Phenomena↗
PubMed1982

Cactus alkaloids. XLVII. N alpha-dimethylhistamine, a hypotensive component of Echinocereus triglochidiatus.

Echinocereus triglochidiatus Engelm. var. neomexicanus (Standley) Standley ex W. T. Marshall is believed to cause psychotropic effects when consumed by the Mexican Tarahumara Indians. A phytochemical study was initiated with E. triglochidiatus Engelm. var. paucispinus Engelm. ex W. T. Marshall, which is more abundant in Texas. In the fractionated extracts three compounds, detected by thin-layer chromatography, were positive to Ehrlich's reagent, indicating the possible presence of indole alkaloids; however, a non-Erhlich positive alkaloid was crystallized as the dihydrochloride and subsequently identified (spectrometrically and via synthesis as N alpha, N alpha-dimethylhistamine dihydrochloride. The same compound was then detected chromatographically in the neomexicanus variety. This compound has peripheral hypotensive effects similar to histamine, and this action may help to explain the alleged psychotrophic effects of the cactus.

Alkaloids↗
PubMed1980

Cactus alkaloids XLII: 3,4-dimethoxy-beta-phenethylamine and heliamine from the Mexican cereoid Backebergia militaris.

Backebergia militaris (Andot) Bravo ex Sánchez Mejorada yielded alkaloid crystals from a fractionated ethanol extract of only 20 g of plant material. The alkaloid was identified as heliamine (6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) hydrochloride. A second alkaloid, 3,4-dimethoxy-beta-phenethylamine hydrochloride, was crystallized after preparative TLC of the mother liquors. Both compounds were isolated previously from other cactus species.

Alkaloids↗
PubMed1977

Cactus alkaloids XXXIII: beta-phenethylamines from the Guatemalan cactus Pilosocereus maxonii.

TLC analysis of extracts of Pilosocereus maxonii (Rose) Byles and Rowley detected six identifiable alkaloids. Preparative TLC aided in the crystallization of the hydrochlorides of N-methyl-3,4-dimethoxyphenethylamine, N-methyl-3-methoxytyramine, and N,N-dimethyl-3-methoxytyramine. Traces of 3,4-dimethoxyphenethylamine (TLC and mass spectrometry), tyramine (TLC), and N-methyltyramine (TLC) were identified. While all of these compounds were isolated and/or detected previously in other cactus species, this study is the first reported crystallization of N-methyl- and N,N-dimethyl-3-methoxytyramine from a natural source.

Alkaloids↗