Biochemical Systematics and Ecology 30 (2002) 65–67

Lignan glucosides from the seeds of Centaureaamericana (Compositae)

Graeme Coopera, Anuszka Lairda, Lutfun Naharb,Satyajit D. Sarkera,*

aSchool of Pharmacy, The Robert Gordon University, Schoolhill, Aberdeen AB10 1FR, Scotland, UKbDepartment of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen,

Aberdeen AB24 3UE, Scotland, UK

Received 14 December 2000; accepted 30 January 2001

Keywords: Centaurea americana; Compositae; Asteraceae; Lignan; Arctiin; Matairesinoside; Phytoecdys-

teroids; Chemotaxonomy

1. Subject and source

Centaurea americana Nutt. (Family: Compositae alt. Asteraceae), an annual,commonly known as ‘‘Jolly Joker’’ or ‘‘Basket flower’’, is indigenous to NorthernAmericaFCoahuila and Nuevo Leon in Mexico and Arizona, Arkansas, Kansas,Louisiana, Missouri, New Mexico, Oklohoma and Texas in the USA, and alsocultivated in several other countries (USDA-ARS-GRIN database, 2000). Seeds ofthis plant (cat. no. 302A) were purchased from an authentic seed supplier, ChilternSeeds, Bortree Stile, Ulverston, Cumbria LA12 7PB, England. A voucher specimen(Centam nashss 200101) has been deposited in the hebarium of the Welsh PlantBreeding Station (WPBS) at IGER, Aberystwyth.

2. Previous work

A sequiterpene lactone, cynaropicrin, has previously been isolated from the aerialparts (Rojatkar et al., 1997; Lindgren, 1966), and phytoecdysteroids have been

*Corresponding author. Tel.: +44-1224-262547; fax: +44-1224-262555.

E-mail address: s.sarker@rgu.ac.uk (S.D. Sarker).

0305-1978/01/$ - see front matter r 2001 Elsevier Science Ltd. All rights reserved.

PII: S 0 3 0 5 - 1 9 7 8 ( 0 1 ) 0 0 0 6 2 - X

detected (by BII bioassay and ecdysteroid specific RIA) in the seeds of C. americana(Sarker et al., 1997a).

3. Present study

Ground seeds (10.00 g) of C. americana were soxhlet-extracted, successively, withn-hexane, dichloromethane and MeOH. The MeOH extract was subjected to Sep-Pak C18 (10 g) column eluting with step gradient: 20%, 40%, 60%, 80% and 100%MeOH in water (100ml each). Preparative-HPLC (C8 preparative column, elutedwith a gradient-water: MeOH=70 : 30 – 00 : 100 in 20min, and then 100% MeOHfor 5min, 10ml/min, monitored by photo-diode-array detector) of the Sep-Pakfraction (40% MeOH) yielded two lignan glucosides matairesinoside (1, 3.6mg)(Rahman et al., 1990; Nishibe et al., 1984) and arctiin (2, 44.6mg) (Rahman et al.,1990; Nishibe et al., 1984). Similar prep-HPLC purification of Sep-Pak fraction(60% MeOH) yielded, in addition to more of arctiin (2, 50.2mg), a phytoecdyster-oid,20-hydroxyecdysone (12.3mg) (Sarker et al., 1997b) and a phenylpropene derivative,3,4-dihydroxycinnamic acid (1.8mg) (SDBS database, 2000). 20-Hydroxyecdysoneand 3,4-dihydroxycinnamic acid were identified by co-HPLC with authentic samples,and also by comparison of their UV and 1H NMR data with published data. Thestructures of the lignan glucosides (1 and 2) have been elucidated unambiguously byUV, optical rotation, FABMS, 1H and 13C NMR analysis, and all these data were ingood agreement with respective literature data .

4. Chemotaxonomic significance

This is the first report on the isolation of lignan glucosides (1 and 2), 20-hydroxyecdysone and 2,3-dihydroxycinnamic acid from C. americana. Both 1 and 2

G. Cooper et al. / Biochemical Systematics and Ecology 30 (2002) 65–6766

are butyrolactone type lignans, and several lignans of this class have previously beenfound in different species of the family Compositae (Dictionary of Natural Products,1999). While arctiin (2) was found in another species, C. imperialis (Dictionary ofNatural Products, 1999), to our knowledge, matairesinoside (1) has never beenreported from any species of the genus Centaurea. However, arctigenin andmatairesinol, the aglycones of 2 and 1, respectively, have been found in several otherspecies of Centaurea, e.g. C. scoparia (Youssef and Frahm, 1995), C. solstitialis(Bruno et al., 1991; Tesevic et al., 1998), C. cuneifolia (Aslan and Oksuz, 1999), C.calcitrapa (Marco et al., 1992), C. dealbata and C. montana (Christensen and Lam,1991a), C. nervosa and C. phrygia (Christensen and Lam, 1991b), etc. Phytoecdys-teroids including 20-hydroxyecdysone have also been found in other species ofCentaurea, and these insect-moulting-hormone-analogues are thought to offer plantssome kind of protections against phytophagous insects (Sarker et al., 1997a).

Acknowledgements

We thank EPSRC National Mass Spectrometry Service Centre (Department ofChemistry, University of Wales Swansea, Swansea, UK) for FABMS analysis andDr. Laurence Dinan (University of Exeter, Exeter, UK) for provision of an authenticsample of 20-hydroxyecdysone.

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