Metabolic Profiling of Peanut Plant Material by LC–TOFMS

There has been an increasing interest in the presence and availability of compounds in plant materials that may possess bioactive properties, in particular, antioxidant activity. Some of these compounds have been attributed to possess anticancer, antiaging, and antimutagenic properties as well as other health benefits (1). The types of plants that have been investigated cover a vast range from common foodstuffs to regional or exotic materials. Plant parts under study have included portions that are traditionally known to be edible, as well as sections that are considered "waste" or used for animal forage. Because most screening techniques involve lengthy separations, high throughput HPLC methods are desirable. LECO's Unique® Time-of-Flight Mass Spectrometer (TOFMS) is an ideal tool for fast separation methods due to its fast acquisition rates of up to 100 spectra per second. Additional features including accurate mass, high full mass range sensitivity and advanced data processing software provide valuable tools for routine identification of components in complex mixtures. LECO's Unique® LC–TOFMS was used to demonstrate these features in the analysis of peanut plant material as described below.

Experimental Conditions

Instrumentation:

• Unique® HT TOFMS with High Flow ESI Source (LECO Corporation):

–Nozzle voltage: (–)160 V

–Desolvation temperature: 300°C

–Electrospray voltage: (–)3500 V

– Desolvation flow (N2): 7.0 L/min

–Interface temperature: 100°C

–Nebulization pressure (N2): 375 kPa

–Data acquisition rate: 1.5 spectra/s

• 1100 Series LC (Agilent Technologies)

–Flow rate: 400 μl /min

–Mobile phase A: 0.1% formic acid in water

–Mobile phase B: acetonitrile/methanol (50:50)

–Gradient: 0 min, 10% B; 30 min, 95%B; 35 min, 95%B; 40 min, 5%B.

–Injection volume: 5.0 ml

–Column temperature: 30°C

–Column: 2.1 × 100 mm, 3mm Restek™ Ultra Aqueous C18

Results and conclusions:

Identification and characterization of different peanut plant organs are of interest in order to determine their potential as functional ingredients in food and nonfood applications. The peanut skin, leaf, root, and shell were compared to identify similarities and differences (Figure 1). Overall, peanut leaf and skin appeared to have the greatest amount of flavonoid and fatty acid content. As antioxidants and protective compounds, it would be consistent with the fact that they are found in the two most exposed organs (exposed to insects, changing soil chemistry, environment, etc.). Also, the antioxidant resveratrol was identified in the shell and root, but not in the skin or leaf. The Unique® LC–TOFMS is a powerful tool for the nontarget screening of peanut plant material. The inherent ability of TOFMS to detect all ions makes it an ideal tool for analysis of unknowns. The automated peak find software and deconvolution feature within ChromaTOF provide clean mass spectra even for coeluting compounds in a complex peanut sample.

Figure 1

Detailed results for the analysis are available upon request.

References

(1)Rice-Evans, C.A., Miller, N.J., Paganga, G., 1996. "Structure-antioxidant activity relationships of flavonoids and phenolic acids." Free Radicals in Biology and Medicine 20: 933–956.

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