Industrial Crops and Products 12 (2000) 93 – 96
Industrial utilization of
Ri
6
ea ornata
seed oil: a moderate
source of vernolic acid
Kallappa M. Hosamani *, Raghavendra M. Sattigeri
P.G.Department of Studies in Chemistry,Karnatak Uni6ersity,Pa6ate nagar,Dharwad580 003,India
Accepted 28 January 2000
Abstract
Ri6ea ornataseed oil was found to contain 12,13-epoxy-octadec-cis-9-enoic acid (vernolic acid, 22.0%) along with the other normal fatty acids like palmitic acid (24.2%), stearic acid (8.9%), oleic acid (17.1%) and linoleic acid (27.8%). The identification and characterization was based on Fourier transform infrared (FTIR),1H-NMR, mass spectrome-try (MS), gas – liquid chromatography (GLC)-techniques and chemical degradations. © 2000 Elsevier Science B.V. All rights reserved.
Keywords:Convulvulaceae;Ri6ea ornata; Seed oil; Fatty acids; Vernolic acid; Normal fatty acids; Industrial utilization
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1. Introduction
Seed oils containing unusual fatty acids are industrially important, as they are used in protec-tive coatings, plastics, plasticizers, dispersants, pharmaceuticals, cosmetics, detergents, soaps, tex-tiles, surfactants, lubricant additives, organic pes-ticides, urethane derivatives and varieties of synthetic intermediates as stabilizers in plastic formulations.
Seed oils containing epoxy fatty acids have been used as stabilizers for plastic formulations and in the preparations of the other long-chain compounds, e.g. Vernonia anthelmintica and V.
roxburghii, species. The epoxidized vegetable seed
oils have some of the properties of polymeric plasticizers but with some aging properties, e.g. soya and linseed oils. Many other types of plasti-cizers continue to be used in major amounts be-cause they can be applied in resins or rubbers other than PVC. The seed oil ofLicania rigidahas attained a commercial status, as it contains enor-mous amount of 4-ketoeleostearic acid. This acid is popular for its drying properties, and, hence, it is used as an ingredient of paints and varnish industries.
In the production of nylon-11, castor oil is transesterified with methanol. The ethoxylated castor oil is the best solubilizer in a multi-compo-nent system. The ethoxylated derivatives of castor oil and hydrogenated castor oil are non-ionic surface-active agents with varied degrees of hy-drophobic – hydrophillic properties. The low level * Corresponding author. Fax: +91-836-747884.
E-mail address:[email protected] (K.M. Hosamani)
K.M.Hosamani,R.M.Sattigeri/Industrial Crops and Products12 (2000) 93 – 96 94
ethoxylated derivatives are water emulsifiable and are used as defoaming agents and de-emulsifiers for petroleum emulsions. The high-level ethoxy-lated products are excellent solubilizers for water-insoluble oils in cosmetic compositions.
The new and interesting unusual fatty acids present in high concentrations in certain seed oils are being exploited for industrial utilization. These fatty acids of unusual structures are highly important for the production of oleochemicals. Considering the extensive applications of such seed oils as an industrial products, an attempt has been made for component fatty acids in Ri6ea
ornataseed oil which could be used as raw materi-als in the production of oleochemicmateri-als in oleo-chemical industries.
Thus,R. ornatais a moderate source of verno-lic acid which shows sufficient promise for its exploitation for industrial utilization. R. ornatais an erect and straggling shrub found in the south-ern part of India. The fleshy flowers are eaten in northern Ceylon. The plant is acrid, pungent and sweetish, and considered to be cooling and a tonic (Kirtikar and Basu, 1933; CSIR, 1938).R.ornata
belongs to the Convulvulaceae plant family which consists of 42 genera and more than 800 species (Cooke, 1967). In view of the above, R. ornata
seed oil has been examined for its component fatty acids. The most interesting finding was the presence of vernolic acid
(12,13-epoxy-octadec-cis-9-enoic acid). An exhaustive survey of the literature reveals that no work has been reported
about the seeds of R.ornata. The present investi-gation describes the occurrence of vernolic acid along with other normal fatty acids in R. ornata
seed oil.
2. Experimental section
The systematic solvent extraction of 100 g of air-dried seeds of R. ornata with light petroleum ether (b.p. 40 – 60°C) in a Soxhlet extractor for 24 h yielded 10 g oil. The seed oil responded to the picric acid thin layer chromatography (TLC) test (Fioriti and Sims, 1968) indicating the probable presence of epoxy fatty acids. However, the seed oil did not respond to the Halphen test (Halphen, 1897), direct TLC test (Hosamani, 1994), and 2,4-dinitrophenyl hydrazine (2,4-DNPH) TLC test (Davis et al., 1969), thereby indicating the absence of cyclopropenoid, hydroxy and keto fatty acids, respectively. The infrared spectra of oil and its methyl esters showed the characteristic absorption band at 825 cm−1 for the presence of epoxy functional group. However, UV and IR spectra of seed oil showed no evidence for trans unsatura-tion or the presence of conjugaunsatura-tion. The analytical values of seed oil so obtained were determined according to the standard American Oil Chemists’ Society (AOCS) methods (Link, 1973) and are listed in Table 1. The Durbetaki titration (Harris et al., 1963) of seed oil at 3°C indicated the presence of 22.2% of total epoxy fatty acids.
3. Acetolysis of epoxide
A portion of the oil (20 g) was stirred overnight at room temperature (27°C) with 80 ml of 10% sulfuric acid in 200 ml of glacial acetic acid as described by Wilson et al. (1961). The acetolyzed product was diluted with distilled water and ex-tracted with ether. The ether extract was thor-oughly washed with distilled water and dried over anhydrous sodium sulfate. The solvent was re-moved in a stream of nitrogen. The saponification of the acetolyzed product was treated with 0.8 N alcoholic potassium hydroxide at room tempera-ture (27°C). After careful acidification of pH 5 Table 1
Analytical values ofR.ornataseed oil
10% Oil content in seeds
Unsaponifiable matter 2% 85 Iodine value
Saponification value 200 Picric-acid TLC test +vea 2,4,-Dinitrophenyl hydrazine −veb
(2,4-DNPH) TLC test
Direct TLC test −veb
−veb Halphen test
22.2% Durbetaki titration at 3°C
Infrared spectrum of seed oil 825 cm−1(For epoxy)
K.M.Hosamani,R.M.Sattigeri/Industrial Crops and Products12 (2000) 93 – 96 95
Table 2
Component fatty acids ofR.ornataseed oil
Percentage
Varian T-60 model instrument using CDCl3 as a solvent. The chemical shifts were measured in parts per million (ppm) downfield from internal TMSi at d=0. The mass spectra were taken on
Finnigan Mat with PDP Micro Computer 810, at 70 eV with a source temperature of 150°C. GLC analysis was carried out on Perkin Elmer Model Sigma Unit using 15% DEGS column on chromo-sorb,W(354 – 250mm) 45 – 60 mesh. The
tempera-tures at injection port, detector port and oven were 240, 240 and 190°C, respectively. Nitrogen flow and chart speed were 30 ml min−1
and 1 cm min−1
, respectively. The machine recorded di-rectly the weight percent of individual peaks. The peaks were identified by comparing their retention times with those of standard reference samples under similar conditions. The melting points were recorded on a Thomas – Hoover capillary melting point apparatus.
6. Results and discussion
Dihydroxy acid obtained from the preparative TLC method was equivalent to 22% by weight of total oil. A concentrate of pure dihydroxy fatty acid (21.9%) was obtained from column chro-matographic techniques. The infrared spectrum of methyl ester of dihydroxy fatty acid showed strong absorption bands at 3450 and 1780 cm−1 for the hydroxyl and ester carbonyl functional groups, respectively. The infrared spectrum also showed characteristic absorption bands at 715 and 1620 cm−1for acisdouble bond. The unsat-urated dihydroxy acid on hydrogenation (Vogel, 1956) with 10% Pd/C gave12,13-dihydroxy-oc-tadecanoic acid, m.p. 96 – 97°C. The unsaturated dihydroxy acid was cleaved with the perman-ganate – periodate method (Von Rudloff, 1956). The GLC analysis of the resulting products as their methyl esters showed that cleavage frag-ments were azelaic acid, m.p. 106 – 107°C (p -bro-mophenacyl ester, m.p. 131 – 132°C) and hexanoic acid (p-bromophenacyl ester, m.p. 70 – 71°C).
The unsaturated dihydroxy acid hadRfvalue as
threo-12,13-dihydroxy oleic acid obtained from the acetolysis of V.anthelmintica seed oil. with 0.5 N sulfuric acid, the liberated mixed fatty
acids were extracted with ether. The ether extract was thoroughly washed with distilled water until neutral and the solvent was removed in a stream of nitrogen.
The separation of these mixed fatty acids into oxygenated and non-oxygenated was accom-plished by the preparative TLC techniques. These fatty acids were examined for the characterization of individual fatty acids. The fatty acids of methyl esters were prepared by Fischer esterification. The gas – liquid chromatography (GLC) analysis was carried out for the non-oxygenated portion. The results are summarized in Table 2.
4. Chromatography
Analytical TLC was performed on glass plates coated with 0.25 or 1.0 mm layers of silica gel ‘G’ using 20 or 30% hexane as the solvent system. The preparative TLC was effected on 20×20 cm plates with 1.0 mm layers of silica gel. When the plates were sprayed with dichlorofluoroscein, the separated bands were clearly visible under ultravi-olet (UV) light. The fatty acids from silica were extracted with ether.
5. Instrumentation
K.M.Hosamani,R.M.Sattigeri/Industrial Crops and Products12 (2000) 93 – 96 96
Scheme 1. Mass spectral fragmentation of methyl 12,13-dihy-droxyoctadec-cis-9-enoate.
Thus, the structure of isolated epoxy fatty acid as dihydroxy fatty acid obtained from R. ornata
seed oil has been characterized as 12,13-epoxyoc-tadec-cis-9-enoic acid (vernolic acid).
References
Cooke, D., 1967. Flora of the Presidency of Bombay, vol. II. Botanical Survey of India, Calcutta, p. 290.
CSIR, 1938. The Wealth of India: Raw materials, vol. IX, Council of Scientific and Industrial Research, New Delhi, p. 48.
Davis, E.N., Wallen, L.L., Goodwin, J.C., Rohwedder, W.K., Rhodes, R.A., 1969. Microbial hydration ofcis-alkenoic acids. Lipids 4, 356 – 362.
Fioriti, J.A., Sims, R.J., 1968. A spray reagent for the identifi-cation of epoxides on thin layer plates. J. Chromatogr. 32, 761 – 763.
Halphen, G., 1897. J. Pharm. Chim. 6, 390.
Harris, J.A., Magne, F.C., Shau, E.L., 1963. Cyclopropenoid fatty acids-II: a step-wise hydrogen bromide titration method for the cyclopropenoid and epoxy derivatives. J. Am. Oil Chem. Soc. 40, 718 – 720.
Hosamani, K.M., 1994.Terminalia chebula seed oil: a minor source of 12-hydroxy-octadec-cis-9-enoic acid: natural products as a source for the food and agricultural indus-tries. J. Sci. Food & Agric. 64, 275 – 277.
Kirtikar, K.R., Basu, B.D., 1933. Indian Medicinal Plants, vol. III. Lalit Mohan Basu, Allahabad, India, p. 1706. Link, W.E. (Ed.), 1973. Official and Tentative Methods of the
American Oil Chemists’ Society, third ed. AOCS, Cham-paign, IL, USA, Methods Da 15 – 48 and DA 16 – 48. Vogel, A.I., 1956. A Text Book of Practical Organic
Chem-istry, third ed. Longmanns, Green & Co., London, p. 866, 950.
Von Rudloff, E., 1956. Oxidations of lipids in media contain-ing organic solvents. Can. J. Chem. 34, 1413 – 1418. Wilson, T.L., Smith, C.R. Jr, Mikolajczak, K.L., 1961.
Char-acterization of cyclopropenoid acids in selected seed oils. J. Am. Oil Chem. Soc. 38, 696 – 698.
The 1H-NMR spectrum of unsaturated dihy-droxy ester gave signals atd5.4 (2H,CH6 CH6 ),
5.0 (m, 2H, 2×CHOH6 , which disappeared on D2O addition), 3.6 (s, 3H, COOCH6 3), 3.5 (m, 2H, CH6 2COOCH3), 2.0 (m, 4H, CH6 2CHCHCH6 2), 1.2 (s, 18H, (CH6 2)9, shielded methylene protons) and 0.9 (t, 3H, termi-nalCH6 3). The saturated dihydroxy methyl ester did not exhibit signals atd 5.4. The other signals
were observed at d 5.0 (m, 2H, 21×CHOH6
which is disappeared on D2O addition), 3.6 (s, 3H, COOCH6 3), 3.5 (m, 2H, 2×CH6 OH), 3.3 (m, 2H,CH6 2COOCH3), 1.2 (s, 28H, (CH6 2)14, shielded methylene protons) and 0.9 (s, 3H, termi-nalCH6 3). The mass spectrum of diacetyl deriva-tive of unsaturated dihydroxy methyl ester showed small molecular ion pleak atm/z412. The allylic cleavage (m/z 197) established a double bond at C9and C10. Thea cleavage on the either side of two acetate groups gave signals at m/z
341, 269, 215, 143 and placed the acetate groups at C12 and C13 (Scheme 1).
