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Journal of Medicinal Plants Research Vol. 3(11), pp. 897-900, November, 2009Available online at http://www.academicjournals.org/jmprISSN 1996-0875 2009 Academic Journals

Full Length Research Paper

Amino acid and GABA content in different cultivars of

Momordica charantia L.Yong Kyoung Kim1, Hui Xu1, Nam IL Park1, Hee Ock Boo2, Sook Young Lee3and Sang Un

Park1*

1Division of Plant Science and Resources, Chungnam National University, 220 Gung-Dong, Yuseong-Gu, Daejeon, 305-

764, Korea.2Department of Biotechnology, Chosun University, 375 Seosuk-Dong, Dong-Gu, Gwangju, 501-759, Korea.

3Research Center for Oral Disease Regulation of the Aged, Chosun University, 375 Seosuk-Dong, Dong-Gu, Gwangju,

501-759, Korea.

Accepted 24 August, 2009

The variability of amino acid levels including gamma-aminobutyric acid (GABA) was investigated in sixcultivars of bitter melon (Momordica charantia L.) of different origins: Nikko and Peacock from Japan,Galaxy and Verde Buenas from Philippines and two native cultivars from China and Korea. Cultivarsvaried considerably in the amounts of different amino acids. Among them, the cultivar Verde Buenasrecorded the highest amounts of seven different amino acids with the content of other amino acids at asatisfactory level. The cultivar Galaxy contained the highest amount of GABA. Second only to VerdeBuenas, the Korean native performed the best, having significantly high levels of five different aminoacids followed by the China native exhibiting the highest amounts of alanine, phenylalanine andproline. Although the cultivar Nikko contained the highest amount of arginine, it recorded the lowestvalues for most of the amino acids. The cultivars Nikko, Peacock and Galaxy did not contain methionineamino acids. These results demonstrated that bitter melon cultivars varied in the amount of differentamino acids and GABA and hence have a high potential as a good source of amino acids and GABA inthe development of food supplements.

Key words:Amino acid, cultivar, gamma-aminobutyric acid, GABA, Momordica charantia L.

INTRODUCTION

Momordica charantia L. is a herbaceous vine belongingto family Cucurbitaceae. This crop is widely grown for itsedible fruit, which is among the most bitter of all vege-tables. All parts of the plant, including the fruit, taste bitterand hence commonly known as bitter melon. It iscultivated throughout the world to use as a vegetable aswell as for its medicinal value. Fruits and seeds of bitter

melon are known to have anti-HIV, anti-ulcer, anti-inflammatory, anti-leukemic, antimicrobial, anti-diabeticand anti-tumor properties (Basch et al., 2003; Shih et al.,2008; Alam et al., 2009; Lii et al., 2009).

Amino acids are organic acids containing both amineand carboxyl functional groups, having a variety of rolesin metabolism. One of the most important functions of

*Corresponding author. E-mail: supark@cnu.ac.kr. Tel: +82-42-821-5730. Fax: +82-42-822-2631.

amino acids is to act as building blocks of proteins. Ahuge amount of different amino acids exist in natureamong them around two dozen of them are vital in humannutrition (Gilani et al., 2008; Millward et al., 2008).

Gamma-aminobutyric acid (GABA, Figure 1) is a non-protein amino acid synthesized via the decarboxylation oL-glutamate in a reaction catalyzed by the cytosolic

enzyme L-glutamate decarboxylase (Forde and Lea2007). It is a valuable component of the free amino acidpool in most prokaryotic and eukaryotic organisms. Invertebrates, GABA is the major neurotransmitter inhibitoin the central nervous system that prevents anxiety andstress-related messages from reaching the motor centersof the brain (Schousboe and Waagepetersen, 2007). Ihas been used to enhance the secretion of growthhormone from the pituitary gland. In addition, it is knownto inhibit the migration of colon carcinoma cells, pavingthe way to the development of specific pharmacologicaagents that delay or inhibit invasion and metastasis of

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NH2

OH

O

Figure 1. Chemical structure of Gamma-aminobutyric acid (GABA).

various cancer types (Enna, 2001; Kowalski et al., 2007;Sarto-Jackson and Sieghart, 2008).

There have been a number of comments as to the rolethat GABA might play in plants including, the involvementin pH regulation, nitrogen storage, plant development anddefense and as a compatible osmolyte as well as analternative pathway for glutamate utilization (Alan andBarry, 1997; Barry et al., 1999).

Most of the research work of bitter melon was doneconsidering its medicinal value but a few researches weredone based on amino acid and GABA content. Theobjectives of this study were to conduct a comparativeanalysis of amino acid and GABA content of differentcultivars of bitter melon form China, Japan, Philippinesand Korea.

MATERIALS AND METHODS

Plant material

Fruits of six different cultivars of M. charantia:(one Korean native,one Chinese native, two Japanse cultivars (Nikko and Peacock

from Japan) and two Philippines cultivars (Galaxy and VerdeBuenas) were collected from the experimental farm of ChungnamNational University (Daejeon, Korea) in September 2008. Freshsamples were stored frozen in sealed clear polyethylene plastic

bags at -80C until used. Collected samples were freeze-dried at -80C for at least 72 h and dried samples were ground into a finepowder (40-mesh) by a mill.

Free amino acid extraction

Amino acids were extracted from freeze-dried plant powder (1 g)with 30 ml of 70% ethanol at 80oC for 20 min. After evaporatingethanol, residue water phase (30 ml) was mixed with ethyl ether (30ml) in a separation funnel. The water phase was separated andfreeze-dried. The extract was resuspended in 3 ml of 0.02 N HCl

and filtered using a 0.45 m syringe filter. The extraction procedurewas replicated three times.

Analysis of amino acids

The amino acid analyzer (HITACHI L-8900, Japan) attachedHITACHI HPLC Packed Column with Ion-exchanging Resin No.2622 PF (4.6 60 mm) and UV detector (VIS1: 570 nm, VIS2: 440nm) was used for analysis of amino acids. Wako L-8500 buffersolution PF-1, 2, 3, 4 and RG were used in this study. Twenty l ofeach sample was injected and determination was performed usingNinhydrin reagent set (Wako Chemical Inc, Japan). All sampleswere run in triplicates.

RESULTS

From the analysis of different cultivars of bitter meloncollected from Korean, China, Japan and Philippinesseventeen different amino acids were found to be invarying proportions (Table 1). The range of detected

amino acid content varied widely irrespective of the placeof origin and the type of cultivar tested. Among all theamino acids isolated, arginine was found to be in remarkably high quantities, while the limiting amino acids werecysteine and methionine. One of the important aminoacids found in large amounts irrespective of cultivar typeis arginine. The mean concentration of arginine wasbetween 28.0 and 52.6 mol/g D.W., which was severatimes significantly higher than any other amino acid foundin this study. The amount of each amino acid varied significantly within a particular cultivar. Among the cultivars ofdifferent locations, the cultivar Verde Buenas containedthe highest amount of seven different amino acids, that

is, aspartic acid, glycine, isoleucine, leucine, methioninethreonine and valine. Besides these seven amino acidsthe same cultivar contained a satisfactory amount oother amino acids. The cultivar Galaxy contained thehighest amount of glutamic acid (5.7 mol/g dry weight(D.W.)) although it contained the lowest amounts ofarginine, aspartic acid, cysteine, lysine and tyrosine. TheKorean native performed the best in terms of five differenamino acids, that is, cysteine, histidine, methionineserine and tyrosine whereas it contained the lowesamounts of Isoleucine and threonine. The Chinese nativecultivars had the highest amount of alanine, phenyl-alanine and proline while arginine content was the lowestThe Japanese cultivar Nikko, although contained the

highest amount of arginine (52.6 mol/g D.W.) recordedthe lowest values for most of the other amino acidscysteine, glutamic acid, glycine, histidine, leucine, phenylalanine, proline, serine and valine. Another Japanesecultivar Peacoak contained the highest amount of lysine(3.7 mol/g D.W.). There was no methionine in thecultivars, Nikko, Peacoak and Galaxy.

The cultivars exhibited significant variability in theiGABA content, varying between 4 - 20 mol/g D.W(Figure 2). The Philippines cultivar Galaxy contained thehighest amount (19.3 mol/g D.W.) of GABA followed bythe Chinese native (14.0 mol/g D.W.) which was aroundfive times more than the other cultivars. The cultivars

Peacock, the Korean native, Verde Buenas and Nikkocontained as low as 3.5, 4.2, 4.8 and 5.2 mol GABA /gdry weight, respectively.

DISCUSSION

Bitter melon contained seventeen amino acids at satis-factory levels, except cysteine and methionine. Amongthem, the amount of arginine (52.6 mol/g D.W.), alanine(21.7 mol/g D.W.) and GABA (19.3 mol/g D.W.) werequite high irrespective of the type of cultivar. As this

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Table 1.Amino acid compositions in the fruit of different cultivars of M. charantia L. (The unit of amino acid content = mol/g dry weight).

Type of aminoacid

Mean Amino Acid Content of Different Cultivars (mol/g D.W.)

Native

(Korea)

Native

(China)

Nikko

(Japan)

Peacoak

(Japan)

Galaxy

(Philippines)

Verde Buenas

(Philippines)

Alanine 4.7 0.6 21.7 1.28 5.3 0.76 4.2 0.4 13.81.5 8.5 1.06

Arginine 28.4 2.1 28.0 3.5 52.6 5.26 48.2 3.2 28.01.8 48.1 6.01Aspartic acid 3.9 0.5 4.4 0.6 4.9 0.7 7.0 1.0 3.5 0.5 7.1 1.0

Cysteine 0.5 0.1 0.2 0.0 0.1 0.0 0.1 0.1 0.1 0.0 0.3 0.0

Glutamic acid 3.4 0.34 5.1 0.5 1.8 0.1 2.3 0.2 5.7 0.5 2.6 0.3

Glycine 1.7 0.17 1.8 0.3 1.2 0.1 2.2 0.1 1.7 0.2 3.3 0.4

Histidine 7.6 0.76 7.4 0.8 3.8 0.5 4.0 0.3 5.9 0.5 7.0 0.8

Isoleucine 2.4 0.20 4.7 0.3 2.5 0.2 5.0 0.4 4.6 0.3 6.4 0.8

Leucine 2.5 0.27 3.2 0.2 1.6 0.1 2.6 0.2 2.7 0.2 3.8 0.4

Lysine 3.0 0.29 3.5 0.7 2.5 0.2 3.7 0.3 2.1 0.1 3.6 0.4

Methionine 0.3 0.29 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.0

Phenylalanine 3.1 0.41 6.1 0.4 2.4 0.1 4.3 0.2 4.2 0.2 6.0 0.7

Proline 2.9 1.46 7.3 1.4 1.5 0.1 1.8 0.2 3.3 0.5 3.0 0.3

Serine 4.9 0.48 4.8 0.3 2.5 0.1 3.1 0.4 3.8 0.3 4.8 0.6Threonine 2.6 0.68 6.8 0.5 9.0 0.5 5.1 0.5 10.1 1.2 12.6 1.5

Tyrosine 7.0 0.60 3.9 0.4 1.9 0.13 3.9 0.4 2.4 0.2 3.1 0.3

Valine 6.8 0.18 9.9 0.9 5. 4 0.4 7.9 1.1 8.4 1.2 11.2 1.4

Figure 2.GABA content in the fruit of different cultivars of M. charantia L. (The unit of GABA content =mol/g dry weight).

vegetables contained almost all of the amino acids insatisfactory amounts, especially with regard to arginine,alanine and GABA, which were in very high, this cropcould be a very good source in the production of arginine,alanine, GABA and other amino acids found in highconcentrations, on a commercial basis.

ACKNOWLEDGEMENTS

This study was carried out with the support of Cooperative Research Program for Agricultural Science andTechnology Development (Project No20070101033118), RDA, The Republic of Korea.

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