Stevenson, Philip C. ORCID: 0000-0002-0736-3619 , Kite, Geoffrey C., Lewis, Gwilym P., Forest, Félix, Nyirenda, Stephen P., Belmain, Steven R. ORCID: 0000-0002-5590-7545 , Sileshi, Gudeta W. and Veitch, Nigel C. (2012) Distinct chemotypes of Tephrosia vogelii and implications for their use in pest control and soil enrichment. Phytochemistry, 78. pp. 135-146. ISSN 0031-9422 (doi:https://doi.org/10.1016/j.phytochem.2012.02.025)

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Abstract

Tephrosia vogelii Hook. f. (Leguminosae) is being promoted as a pest control and soil enrichment agent for poorly-resourced small-scale farmers in southern and eastern Africa. This study examined plants being cultivated by farmers and found two chemotypes. Chemotype 1 (C1) contained rotenoids, including deguelin, rotenone, sarcolobine, tephrosin and α-toxicarol, required for pest control efficacy. Rotenoids were absent from chemotype 2 (C2), which was characterised by prenylated flavanones, including the previously unrecorded examples (2S)-5,7-dimethoxy-8-(3-hydroxy-3-methylbut-1Z-enyl)flavanone, (2S)-5,7-dimethoxy-8-(3-methylbut-1,3-dienyl)flavanone, (2S)-4′-hydroxy-5-methoxy-6″,6″-dimethylpyrano[2″,3″:7,8]flavanone, (2S)-5-methoxy-6″,6″-dimethyl-4″,5″-dihydrocyclopropa[4″,5″]furano[2″,3″:7,8]flavanone, (2S)-7-hydroxy-5-methoxy-8-prenylflavanone, and (2R,3R)-3-hydroxy-5-methoxy-6″,6″-dimethylpyrano[2″,3″:7,8]flavanone. The known compounds (2S)-5-methoxy-6″,6″-dimethylpyrano[2″,3″:7,8]flavanone (obovatin 5-methyl ether) and 5,7-dimethoxy-8-(3-hydroxy-3-methylbut-1Z-enyl)flavone (Z-tephrostachin) were also found in C2. This chemotype, although designated Tephrosia candida DC. in collections originating from the World Agroforestry Centre (ICRAF), was confirmed to be T. vogelii on the basis of morphological comparison with verified herbarium specimens and DNA sequence analysis. Sampling from 13 locations in Malawi where farmers cultivate Tephrosia species for insecticidal use indicated that almost 1 in 4 plants were T. vogelii C2, and so were unsuitable for this application. Leaf material sourced from a herbarium specimen of T. candida contained most of the flavanones found in T. vogelii C2, but no rotenoids. However, the profile of flavonol glycosides was different to that of T. vogelii C1 and C2, with 6-hydroxy-kaempferol 6-methyl ether as the predominant aglycone rather than kaempferol and quercetin. The structures of four unrecorded flavonol glycosides present in T. candida were determined using cryoprobe NMR spectroscopy and MS as the 3-O-α-rhamnopyranosyl(1 → 6)-β-galactopyranoside-7-O-α-rhamnopyranoside, 3-O-α-rhamnopyranosyl(1 → 2)[α-rhamnopyranosyl(1 → 6)]-β-galactopyranoside, 3-O-α-rhamnopyranosyl(1 → 2)[α-rhamnopyranosyl(1 → 6)]-β-galactopyranoside-7-O-α-rhamnopyranoside, and 3-O-α-rhamnopyranosyl(1 → 2)[(3-O-E-feruloyl)-α-rhamnopyranosyl(1 → 6)]-β-galactopyranosides of 6-hydroxykaempferol 6-methyl ether. Tentative structures for a further 37 flavonol glycosides of T. candida were assigned by LC–MS/MS. The correct chemotype of T. vogelii (i.e. C1) needs to be promoted for use by farmers in pest control applications.

Item Type:	Article
Additional Information:	[1] Available online: 4 April 2012. [2] Published in print: June 2012. [3] Published as: Phytochemistry, (2012), Vol. 78, pp. 135–146. [4] Phytochemistry - is an official journal of the Phytochemical Society of Europe and the Phytochemical Society of North America.
Uncontrolled Keywords:	tephrosia vogelii, tephrosia candida, leguminosae, flavanones, dihydroflavonol, flavonol glycosides, rotenoids, pesticidal plants
Subjects:	S Agriculture > S Agriculture (General)
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science > Natural Resources Institute Faculty of Engineering & Science > Natural Resources Institute > Agriculture, Health & Environment Department
Related URLs:	Publisher Organisation Organisation
Last Modified:	03 Jul 2013 16:01
URI:	http://gala.gre.ac.uk/id/eprint/8188

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