Elaine A. Porter

Calystegines in Solanum and Datura species and the death's-head hawk-moth (Acherontia atropus)

Abstract Polyhydroxylated tropane alkaloids, not hitherto recorded from the potato ( Solanum tuberosum ), were detected in the leaves and tubers of this plant. They are potent inhibitors of glycosidases and may be responsible for neurological disorders in livestock. These alkaloids were also extracted from a sphingid moth and an ithomiine butterfly, the larvae of which feed on Solanum .

Chemical basis for resistance in sweetpotato Ipomoea batatas to the sweetpotato weevil Cylas puncticollis

The aim of this work was to determine the basis of resistance in a sub-Saharan sweetpotato variety, New Kawogo, to the African sweetpotato weevil Cylas puncticollis. This insect feeds on the roots, reducing quality and yield, and is the most important production constraint of sweetpotato in Africa. Laboratory bioassays were designed to determine how the performance of weevils differed on susceptible and resistant roots. Subsequently, liquid chromatography-mass spectrometry (LC-MS) analysis of the root surface and root latex identified quantitative and qualitative differences in the chemical profiles with higher levels of octadecyl and hexadecyl esters of hydroxycinnamic acids reported in the resistant variety. The compounds were synthesized to confirm their identity and incorporated into artificial diets for bioassays on C. puncticollis. High levels of mortality and developmental inhibition were recorded for larvae feeding on treated diets, and the effect was dose-dependent. Thus, in contrast to previous work on resistant African sweetpotato cultivars, resistance in New Kawogo is not only active, but is quantifiable and manageable for breeding. Work is underway to determine what effect these compounds have on the weevils at a molecular level. The inheritance of the root latex esters will be studied in new crosses and mapped in new populations using quantitative trait loci (QTLs) that are currently being developed.

High performance liquid chromatography quadrupole ion trap and gas chromatography/mass spectrometry studies of polyhydroxyalkaloids in bluebells

A crudely purified polyhydroxyalkaloid (PHA) extract of Hyacinthoides non-scripta (Hyacinthaceae) was studied by gas chromatography/mass spectrometry (GC/MS), liquid chromatography/sequential mass spectrometry (LC/MSn) and direct infusion atmospheric pressure chemical ionisation-mass spectrometry (APCI-MS) to determine the best method for screening plant extracts for PHAs. Direct infusion was determined to be the technique of choice to carry out rapid screening, whereas LC/MS has the potential to reveal isomeric compounds with appropriate high performance liquid chromatography (HPLC) separation, and we report here a successful HPLC separation of underivatised PHAs in a crude extract. The requirement to derivatise PHAs for GC/MS analysis was found to confuse screening due to the formation of multiple derivatives. Also, the electron ionization (EI) mass spectra were of limited diagnostic value and GC/MS failed to detect high molecular weight PHA derivatives such as those of PHA-diglycosides. Two glycosides not previously reported in Hyacinthaceae were detected by direct infusion APCI-MS. Copyright

Phenolic profile characterization of Chemlali olive stones by liquid chromatography-ion trap mass spectrometry.

Aqueous methanol extracts of Chemlali olive stones were analyzed by reverse phase high-performance liquid chromatography (HPLC) with diode array detection and mass spectrometry [LC-MS/MS]. Oleoside, oleoside 11-methyl ester, nuezhenide, oleoside 11-methyloleoside, nuezhenide 11-methyloleoside, oleuropein, and glycosides of tryosol and hydroxytyrosol glycosides were identified in stones of Chemali olives. The antioxidant activity observed for the extract of the olive stones (IC50 = 13.84 μg/mL, TEAC = 0.436 mM) may be due to the high content of phenolic compounds, of which the main compounds are nuezhenide (325.78 mg/100g), methoxy derivative of nuezhenide (132.46 mg/100g), and nuezhenide-11-methyloleoside (82.91 mg/100g). These results suggest the use of olive stones as sources of natural antioxidants.

Enhanced profiling of flavonol glycosides in the fruits of sea buckthorn (Hippophae rhamnoides).

Use of enhanced LC-MS/MS methods to identify common glycosyl groups of flavonoid glycosides enabled better characterization of the flavonoids in fruits of sea buckthorn (Hippophae rhamnoides). The saccharide moieties of 48 flavonol O-glycosides detected in a methanol extract were identified by these methods. Several of the flavonol glycosides were acylated, two of which were isolated and found to be new compounds. Their structures were determined using spectroscopic and chemical methods as isorhamnetin 3-O-(6-O-E-sinapoyl-β-D-glucopyranosyl)-(1→2)-β-D-glucopyranoside-7-O-α-L-rhamnopyranoside (24) and isorhamnetin 3-O-(6-O-E-feruloyl-β-D-glucopyranosyl)-(1→2)-β-D-glucopyranoside-7-O-α-L-rhamnopyranoside (30). Analysis of the acylated glycosyl groups of 24 and 30 by serial mass spectrometry provided evidence to suggest the acylation position of 11 other minor flavonol glycosides acylated with hydroxycinnamic or hydroxybenzoic acids. The nitric oxide scavenging activities of 24 and 30 were compared with those of other flavonoids and with ascorbic acid and the potassium salt of 2-(4-carboxyphenyl)-4,5-dihydro-4,4,5,5-tetramethyl-1H-imidazolyl-1-oxy-3-oxide (carboxy-PTIO).

Electrospray and APCI analysis of polyhydroxyalkaloidsusing positive and negative collision induced dissociation experiments in aquadrupole ion trap

Atmospheric pressure chemical ionisation (APCI) and electrospray (ES) are compared as ion sources in the analysis of polyhydroxyalkaloids (PHAs) by liquid chromatography mass spectrometry (LC-MS) and collision induced dissociation (CID) product ion spectra, from tandem mass spectrometry (MS-MS) experiments in a quadrupole ion trap, are reported for 12 naturally occurring PHAs. APCI was found to be a more useful source than ES, as APCI could be used to generate deprotonated molecule ions in negative mode and for some isomeric PHAs the negative CID product ion spectra were more diagnostic than the positive product ion spectra. On-column detection limits were also approximately 32 times lower by positive APCI than ES. The work provides data that will facilitate screening and characterisation of this group of important natural products in plant and fungal extracts.

Acyl spermidines in inflorescence extracts of elder (Sambucus nigra L., Adoxaceae) and elderflower drinks.

LC-UV-MS analyses of inflorescence extracts of Sambucus nigra L. (elder, Adoxaceae) revealed the presence of numerous acyl spermidines, with isomers of N,N-diferuloylspermidine and N-acetyl-N,N-diferuloylspermidine being most abundant. Pollen was the main source of the acyl spermidines in the inflorescence. Three of the major acyl spermidines were isolated and their structures determined by NMR spectroscopy as N⁵,N¹⁰-di-(E,E)-feruloylspermidine and the new compounds N¹-acetyl-N⁵,N¹⁰-di-(Z,E)-feruloylspermidine and N¹-acetyl-N⁵,N¹⁰-di-(E,E)-feruloylspermidine. An isomer of N,N,N-triferuloylspermidine was also obtained and identified as N¹,N⁵,N¹⁰-tri-(E,E,E)-feruloylspermidine. In addition to stereoisomers of the isolated acyl spermidines, other acyl spermidines detected by the positive ion LC-UV-MS were isomers of N-caffeoyl-N,N-diferuloylspermidine, N-coumaroyl-N,N-diferuloylspermidine, N-caffeoyl-N-feruloylspermidine, N-coumaroyl-N-feruloylspermidine, N-acetyl-N-caffeoyl-N-feruloylspermidine, and N-acetyl-N-coumaroyl-N-feruloylspermidine. Analysis of commercial elderflower drinks showed that acyl spermidines were persistent in these processed elderflower products. Examination of inflorescence extracts from Sambucus canadensis L. (American elder) revealed the presence of acyl spermidines that were different from those of S. nigra.

Rapid detection of polyhydroxyalkaloid mono- and diglycosides in crude plant extracts by direct quadrupole ion trap mass spectrometry

Direct MS analysis, utilizing first-order MS and subsequent MS2 and MS3 product ion analyses, is shown to provide a rapid means of characterizing polyhydroxyalkaloid glycosides and aglycones in aqueous methanol plant extracts that have been crudely purified on ion exchange resin. Analysis of species known to synthesize polyhydroxyalkaloids resulted in the discovery of the first diglycosides of these compounds. These were detected in Omphalea diandra and Syzygium oleosum. A monoglycoside was also detected as a minor component in Castanospermum australe. Copyright

Variation of theanine, phenolic, and methylxanthine compounds in 21 cultivars of Camellia sinensis harvested in different seasons

This is the first study to use chemometric methods to differentiate among 21 cultivars of Camellia sinensis from China and between leaves harvested at different times of the year using 30 compounds implicated in the taste and quality of tea. Unique patterns of catechin derivatives were observed among cultivars and across harvest seasons. C. sinensis var. pubilimba (You 510) differed from the cultivars of C. sinensis var. sinensis, with higher levels of theobromine, (+)-catechin, gallocatechin, gallocatechin gallate and theasinensin B, and lower levels of (-)-epicatechin, (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG), respectively. Three cultivars of C. sinensis var. sinensis, Fuyun 7, Qiancha 7 and Zijuan contained significantly more caffeoylquinic acids than others cultivars. A Linear Discriminant Analysis model based on the abundance of 12 compounds was able to discriminate amongst all 21 tea cultivars. Harvest time impacted the abundance of EGC, theanine and afzelechin gallate.