Roger D. Waigh

Secoiridoid and triterpenic acids from the stems of Nauclea diderrichii

Abstract The stem bark of Nauclea diderrichii has yielded diderroside, a new secoiridoid glucoside, as well as quinovic acid, 3-oxoquinovic acid and 3- O -glucosylquinovic acid. The hydrocarbon fraction was dominated by n -heptacosane and n -nonacosane, which accords with the predominance of n -octacosanoic acid in the alkanoic acid fraction.

A Convenient Procedure for the Reductive Desulphurisation of Thioethers with Nickel Boride

Abstract Nickel boride, conveniently prepared in situ from nickel (II) chloride hexahydrate and sodium borohydride, cleanly desulphurises thioethers in excellent yields.

Parabolic structure-activity relationships: a simple pharmacokinetic model.

Wallace, S. M. (1978) J. Pharm. Sci. 67: 1547-1550 Kappas, A, , Anderson, K. E., Conney, A. H.. Alvares, A. P. (1976) Clin. Pharmacol. Ther. 20: 643-653 Norris, W., Telfer, A. B. M. (1969) Br. J. Anaesth. 41: 874-876 Notari, R. E., De Young, J. L., Anderson, K. E. (1975) Biopharmaceutics and Pharmacokinetics. An Introduction. Second Edition. Marcel Dekker Inc. New York. Nowak, H., Schorre, G.. Struller. R. (1966) Arzneim. Forsch. 16: 407-411 Parmar, S. S . , Ali, B., Brumleve. S . J . , De Boer, B. (1974) Pharmacologist 16: 238 Pascarelli, E. F. (1973) J . Am. Med. Assoc. 224: 1512-1514 Prabhu, V. G. Browne, R. K., Zaroslinski, J . F. (1964) Int. Pharmacodyn. Ther. 148: 228-236 Prabhu, V. G., Parikh, S. H., Shah, G. F. (1967) Indian J. Med. Sci. 21: 524-532 Preuss, Fr. R., Hassler, H. M., Kopf, R. (1966) Arzneim.Forsch. 16: 401407 Seth, P. K., Srivastava, S. P., Agarwal, D. K., Mushtaq, M. (1977) Bull. Environ. Contam. Toxicol. 17: 727-732 Temant, S. F. Jr. (1973) Br. J. Addict. 68: 327-330

Cis-avicennol, a new pyranocoumarin from the root bark of Zanthoxylum elephantiasis

Abstract A new pyranocoumarin has been isolated from the root bark of Zanthoxylum elephantiasis and identified as cis -avicennol (6-(3-hydroxy-3-methyl- cis -but-1-enyl)-5-methoxy-2,2-dimethyl- 2 H -benzo [1,2b:3,4b′] dipyran-8-one) on the basis of comparison of spectral data with that of trans -avicennol and conversion to tetrahydroavicennol. The usefulness of the lanthanide shift reagent Eu(fod) 3 in the assignment of cis configuration to the butenyl sidechain is briefly discussed.

Three diterpenes with a secolabdane skeleton from Clutia abyssinica

Abstract The roots of Clutia abyssinica have yielded three new diterpenes with a 6,7-secolabdane skeleton. Detailed structural assignments have been made from high-field NMR data, particularly nuclear Overhauser effects.

TEN 5-METHYLCOUMARINS FROM CLUTIA ABYSSINICA

Abstract The chloroform extract of the powdered whole root of Clutia abyssinica has yielded a complex mixture of 5-methylcoumarins, of which 10 have been isolated in pure form and identified, mostly by NMR.

A RAPID METHOD FOR THE IDENTIFICATION OF FATTY ACID AND STEROL CONSTITUENTS OF COMPLEX STEROL ESTER MIXTURES

Sterol esters are comon plant products and are frequently encountered as complex mixtures. Three or four sterols may be esterified by ten or more fatty acids, so that most constituents are present in very small quantities. We have examined the sterol ester fraction of the petrol extract from the stem bark of Nauclea diderrichii (Rubiaceae), which presents the characteristic difficulties. Sitosterol palmitate had previously been reported from this species (King and Jurd 1953).

Application of the WATR technique for water suppression in 1H NMR spectroscopy in determination of the kinetics of hydrolysis of neostigmine bromide in aqueous solution.

Abstract— Both ammonium chloride and guanidinium chloride were used to secure water suppression in 1H NMR spectra using the ‘Water Attenuation by T2 Relaxation’ (WATR) technique. The effect of phosphate buffer in the suppression was investigated over a range of pH values at 80 MHz. The spin‐spin relaxation time of water protons at 80 MHz was found to reach a minimum at pH 7·3 in the presence of 0·1 m phosphate buffer and 1 m guanidinium chloride; these conditions were therefore chosen for subsequent use of the WATR technique in a study of the kinetics of hydrolysis of neostigmine bromide. The method was found to be very convenient for studies of the hydrolysis of this representative amide.

Gastrointestinal transit studies in the rat using 19F-NMR

Abstract 19 F-NMR has been used to assess the movement of a non-disintegrating pellet containing a fluorinated derivative of pentaerythritol in the gastrointestinal tract of a rat. The data were treated using computer graphics to provide a three-dimensional representation of the movement of the pellet.

1H NMR as an analytical tool for the investigation of hydrolysis rates: a method for the rapid evaluation of the shelf-life of aqueous solutions of drugs with ester groups

Abstract— The rate of hydrolysis of esters of primary and secondary alcohols can be determined quickly and easily by 1H NMR in aqueous solution, provided that the water signal is suppressed by the WATR (Water Attenuation by T2 Relaxation) method. To evaluate this approach, Arrhenius plots have been constructed for hydrolysis of acetylcholine, carbachol and atropine, and the effect of pH on the hydrolysis of procaine has been determined over a limited range. The results agree well with literature values for rate constants.