MAIN COhlPO?TENTS IK' CEREUS P E R U V I A N U S E PI CU TI CU LAR W,4X
-issTRicT.-The epicuticular wax of Cereus perurinnus (L.) &filler was analyzed. The main fractions are hydrocarbons (with C B Ipredominating) and esters.
Cactaceae, a botanical family original to the Sen- World, is particularly n-ell adapted to arid climates (1). Photosynthesis in cacti, which follom the CAM pathway ( 2 ) , can proceed at internal temperatures 15' above the ambient temperature ( 3 ) . This is achieved while very low tranqpirational rates are maintained ( 3 ) through daytime stomatal closure (2) and with contributions from other protective systems ( 2 , 4). One of these is the epicuticular wax layer, which has been established to be an adaptation of plants to dry climates ( 5 ) . Cereus perucialzus is a columnar Cactaceae native to southeastern South America. It belongs to the tribe Cereeae, which includes over three-fourths of all cacti species (1). C. p e r u t i a m s 11-as the first of the group to be described (by Tabernaemontanus in his Kreuterbuch, in AD 1625 (l)), and the name refers to the candelabrum-like branching of the species. This report presents the first detailed analytical results for waxes from this family, there only being previous reports by Chibnall et al. for a sample from an unspecified Opzuitia (6, 7 ) (the main components of that wax were described as the C3:, C33and CBi hydrocarbons and the Czsand C30 n-alkanols, and n-ere detected by indirect means) and by Herbin et al. (8) for the hydrocarbons of Harrisia marti& (the main components were the C37, C35, C33and C39 homologues).
RESULTS ASD DISCUSSIOK The total mix extracted represented 0.1% of the fresh plant material, an average of 1.5 rnglcmz of plant surface. This is high 11-lien compared n i t h similar data for other plants (9). The isolated wax ha. a melting range of 38-63'. Column chromatography and preparative tlc n-ere used to qeparate the different fractions. m-liich include: hydrocarbons (657,), esters (lo%), sterols (6%), free acids (5%), free alkanols (3%) and an as yet unidentified fraction (10%). The composition of the hydrocarbon, ester and free fatty acid fractions n-ere determined by glc and are summarized in table 1. The preponderance of the hydrocarbon fraction is quite marked, being higher than that in mobt xixes. including candelilla (57%) , esparto (60%) and Pisuin satizuin (617,) naxes (lo), but loner than that reported for Solaizdra graizdijora (927,) (8. 11). The main component in thiq fraction is the C3l homologue, something usual in plant n-axe9 ( I I ) , but different from v-hat is described for other cacti 11-axes (6, '7, 8 ) . The acid components, both in the ester and free fatty acid fractions, show a distribution with tn o superinipoqed serieq: a lo^ molecular n-eight series n-ith CI6 and CIS as main constituents; and a high molecular n-eight series, with C Z ~ and CZsaq principal members. The free fatty acid fraction ha3 mono-unsaturated constituents. not present as esters. The ester fraction has the C28, Cz6 and C ~ O I D E Y I S S.R L.;c o X i s s t s i p t 1634 A p t o . 10.4, Illowtezzdeo, l - r i ( g u a 3 . 2Facultad de Qztinitca, M o n f e ; t d e o , L-rugzra). 564
SEP-OCT
19801
HUGHES ET AL.
:
565
EPICUTICULAR WAX
TABLE 1. Composition of C. peruz'ianzts epicuticular wax. (Weight
5 determined by gas liquid chromatography). I
Sumber of carbon atoms
Hydrocarbons
'
Hydrolysis products of esters I
n-acids 12 13 14 15 16 16:l 17 18 18:l 19 20 2O:l 21 22 23 24 25 26 27 28 29 30 31 32 33
-
n-alkanols
Free acids
1
-
1
-
29
-
1 17
ii
18 tr 2 1 2 2 1
-
1 17 -
1 7
~
1 1
1 5
3
2 10 2
1
12 2 24 1 54 1 tr
5
14
0
I
-
3 -
-
-
-
5
I
-
I
n-alkanols as main components. This is similar to that found by Chibnall et (6, 7 ) in Opzinfia sp.
aZ.
EXPERIMESTAL COLLECTIOS OF THE n-.ix.-Cereus perur iaxzis (L.) Niller (I) n as collected at Punta Ballena (llaldonado. Cruguay), in January 19'75. h voucher .ample n as kept as S o . 106 in 3Ir. Niguel A. lluriel'q Cactaceae Collection (Montevideo, Uruguay). The extraction of the u-ax n-as completed by dipping the fresh plant material in chloroform (15 seconds. to exclude internal lipids). The reculting chloroform solution n as filtered and the chloroform n as removed by evaporation.
SEPARATIO\ OF F R A C T I O S R . - ~ ~ sample of the v a x (1.34 g) \vas applied on a Silica Gel column (Iiieselgel. Koelm. 0.063-0.2 nini; '75 g). Hydrocarbon. ( S i 0 mg) n-ere eluted n-ith hexane (350 nil) : ester- (13.5 mg) n i t h hexane-chloroform (4:l; 5C10 nil); an unidentified fraction (130 mg) n i t h a cecond fraction of hexanechloroform ( 2 : l : 300 nil) : and a complex fraction 1200 mg) Tt-itli chloroform. Thiz complex fraction (105 mg) n a s separated by preparatire tlc (llerck HF; 20 cm) n i t h chloroform a. aolvent. By repeated chromatography free fatty acids (45 mg. 6% of original nax). free alkanols (38 mg. .5TGof wax) and sterols (22 mg. 3 5 of nax) n-ere icolated.
THIS LAI ER CHRO\IATOGRAPHY-T~C was performed with Silica Gel plates (llerck G; 0.25 mm t1iickne.q: 20 em) with petroleum ether 60-SOo-diethj-l ether-
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JOURSAL O F NATURaL PRODUCTS
[VOL. 43,
NO.
5
acetic acid (90:10:2) or chloroform as solvents. The plates were developed by use of sulfuric acid spray and charring. The different fractions were identified by comparison with standards of known composition. GAS LIQUID CHROhIBTOGRAPHT.-GaS chromatograms were run on a PyeGnicam model 104 gas chromatograph following established procedures (12, 13). The hydrocarbons were identified by use of the C27 synthetic homologue as internal standard. The methyl esters and the acetates were prepared according to standard procedures (12, 13) and identified by comparison against pure standards. The isolated free fatty acids were methylated u-ith diazomethane. ACKSOWLEDGRIESTS The authors wish t o thank the British and Japanese embassies in RIontevideo for important donations and the Sigma Xi society for a grant t h a t made this work possible. The invaluable collaboration of Mr. hl. A. Muriel is dutifully acknowledged. Receieed 19 Septeniber 1979.
LITERATURE C I T E D 1. N. L. Britton and J. S . Rose. The Cactaceae. W'ashington D.C. 1920. Carnegie Institution. 2. S. R . Szarek and J . H . Troughton, Plaizt Physzol., 58, 367 (1976). 3. 1%'. K. Smith, Sciewce, 201, 614 (1978). 4. P. Lloyna and R . Tubio, Planfa M e d i c a , 32, 201 (1977). 5 . G. Eglinton and R . J. Hamilton, Sczence, 156, 1322 (1967). 6. A. C. Chibnall, S.H. Piper, A. Pollard, E. F. Williams and P . T.Sahai, Bqociien?. J . , 28, 2189 11934). 7 . J . D. Waldron, D . S. Gowers, A4. C. Chibnall and S.H. Piper, Biociient. J . , 78, 435 (1961). 8. G. -4.Herbin and P . A . Robins, Piiyfochenizsiry, 7, 256 (1968). 9. E. A. Baker, J. Procopiou and G. 31.Hunt, J . Sci. F d . Aerzc., 26, 1093 (1975). 10. P . J. Holloway, J . Sc;. Fd. rlgrzc., 20, 124 (1969). 11. G. -4.Herbin and P. A. Robins, Piiyfociieni7sfry, 8, 1986 (1969). 12. E. Soler, P. 1Ioyna and G. Ramos, L l o j d i a , 41, 71 (1978). 13. P. Moyna, G. Ranios and J. Toth, Piiyfocheinzsfry,17, 556 (1978).
