(+/-)-catechin: chemical weapon, antioxidant, or stress regulator?
(+/-)-Catechin is a flavan-3-ol that occurs in the organs of many plant species, especially fruits. Health-beneficial effects have been studied extensively, and notable toxic effects have not been found. In contrast, (+/-)-catechin has been implicated as a 'chemical weapon' that is exuded by the roots of Centaurea stoebe, an invasive knapweed of northern America. Recently, this hypothesis has been rejected based on (+/-)-catechin's low phytotoxicity, instability at pH levels higher than 5, and poor recovery from soil. In the current study, (+/-)-catechin did not inhibit the development of white and black mustard to an extent that was comparable to the highly phytotoxic juglone, a naphthoquinone that is allegedly responsible for the allelopathy of the walnut tree. At high stress levels, caused by sub-lethal methanol concentrations in the medium, and a 12 h photoperiod, (+/-)-catechin even attenuated growth retardation. A similar effect was observed when (+/-)-catechin was assayed for brine shrimp mortality. Higher concentrations reduced the mortality caused by toxic concentrations of methanol. Further, when (+/-)-catechin was tested in variants of the deoxyribose degradation assay, it was an efficient scavenger of reactive oxygen species (ROS) when they were present in higher concentrations. This antioxidant effect was enhanced when iron was chelated directly by (+/-)-catechin. Conversely, if iron was chelated to EDTA, pro-oxidative effects were demonstrated at higher concentrations; in this case (+/-)-catechin reduced molecular oxygen and iron to reagents required by the Fenton reaction to produce hydroxyl radicals. A comparison of cyclic voltammograms of (+/-)-catechin with the phytotoxic naphthoquinone juglone indicated similar redox-cycling properties for both compounds although juglone required lower electrochemical potentials to enter redox reactions. In buffer solutions, (+/-)-catechin remained stable at pH 3.6 (vacuole) and decomposed at pH 7.4 (cytoplasm) after 24 h. The results support the recent rejection of the hypothesis that (+/-)-catechin may serve as a 'chemical weapon' for invasive plants. Instead, accumulation and exudation of (+/-)-catechin may help plants survive periods of stress.
Chobot
Vladimir
V
Department of Chemical Ecology and Ecosystem Research, University of Vienna, Vienna 1090, Austria.
Huber
Christoph
C
Trettenhahn
Guenter
G
Hadacek
Franz
F
D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D001156:Artemia / Q000187:drug effects; D002392:Catechin / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D003603:Cytotoxins / Q000494:pharmacology; D003855:Deoxyribose / Q000378:metabolism; D005638:Fruit / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009149:Mustard Plant / Q000254:growth & development; D009285:Naphthoquinones / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism
D000975:Antioxidants; D003603:Cytotoxins; D009285:Naphthoquinones; D017382:Reactive Oxygen Species; D003855:Deoxyribose; D002392:Catechin; C005134:juglone
Plant Cell Environ. 2009 Feb;32(2):158-69
19021890
Oecologia. 2009 Apr;159(4):803-15
19219462
Bioessays. 2006 Nov;28(11):1091-101
17041898
Fitoterapia. 2006 Apr;77(3):194-8
16488556
Biochem J. 1997 Mar 15;322 ( Pt 3):681-92
9148737
Free Radic Biol Med. 1999 Oct;27(7-8):873-81
10515592
Sci Total Environ. 1982 Feb;22(3):213-34
7043732
Plant Signal Behav. 2009 May;4(5):422-4
19816095
J Chem Ecol. 2009 Feb;35(2):141-53
19153796
FEMS Microbiol Rev. 2008 May;32(3):501-21
18371173
Biosci Biotechnol Biochem. 1996 Jan;60(7):1131-5
27299714
New Phytol. 2005 Jan;165(1):9-28
15720617
Free Radic Res. 2002 Nov;36(11):1199-208
12592672
Science. 2003 Sep 5;301(5638):1337-8
12958350
J Chem Ecol. 2009 Mar;35(3):383-90
19263168
Plant Physiol. 2006 Jun;141(2):312-22
16760481
J Chem Ecol. 2003 Nov;29(11):2397-412
14682522
Science. 2003 Sep 5;301(5638):1377-80
12958360
J Chem Ecol. 2006 Oct;32(10):2327-31
16955253
J Theor Biol. 2008 Aug 7;253(3):625-7
18514229
J Chem Ecol. 2007 Jul;33(7):1456-66
17577597
Biochim Biophys Acta. 2005 Jan 18;1721(1-3):174-84
15652192
Anal Biochem. 1987 Aug 15;165(1):215-9
3120621
Environ Pollut. 2006 Nov;144(2):453-62
16677747
Z Naturforsch C J Biosci. 2008 Jul-Aug;63(7-8):476-82
18810988
Environ Toxicol Pharmacol. 1999 Dec;8(1):15-21
21781937
Free Radic Biol Med. 2006 Mar 15;40(6):968-75
16540392
Trends Plant Sci. 2007 Mar;12(3):125-34
17293156
J Agric Food Chem. 2008 May 28;56(10):3706-13
18435537
J Agric Food Chem. 2009 May 13;57(9):3780-5
19296660
Anal Biochem. 1998 Mar 1;257(1):40-4
9512770
Arch Biochem Biophys. 2008 Aug 15;476(2):102-6
18358827
New Phytol. 2007;173(4):852-860
17286833
Trends Plant Sci. 2007 Mar;12(3):98-105
17287141
Appl Environ Microbiol. 2002 Jan;68(1):143-51
11772620
Biochem J. 1993 Mar 15;290 ( Pt 3):693-9
8457196
J Agric Food Chem. 2003 Sep 10;51(19):5798-802
12952436
Curr Opin Plant Biol. 2008 Oct;11(5):530-5
18722804
Free Radic Biol Med. 1995 May;18(5):919-22
7797101
Physiol Plant. 2008 Jul;133(3):481-9
18346071
PLoS One. 2008 Jul 02;3(7):e2536
18648546