Sesquiterpene alcohols of the copane series from essential oil of Ocimum americanum

Short Reports 2. Perry, L. M. (1980) in Medicinal Plants ofEast and South East Asia, p. 96. MIT Press, Cambridge, USA. 3. Sastri, B. M. (1948) in The Wealth ofIndia, A Dictionary of Indian Raw Materials and Industrial Products, Vol. VIII, CSIR, Delhi. 4. Pongboonred, S. (1971) in Maiter Meang Thai, p. 117. Kasembunakij Press, Bangkok. 5. Bonorino, U. C., Gonalons, G. P., Basile, A. R., Zunino, H. and Lacour, J. J. (1937) Bol. Acad. Nat. Med. (Buenos Aires)

691

6. Rivera, I. (1943) An. Inst. Biol. Mex. 14, 38. 7. Sibabrata, M., GeolTery, C. A., Nisir, R., Supreeya, R., Payom, T. and Hylands, P. J. (1983) J. Nat. Prod. 46, 671. 8. Ahmad, V. U. and Fizza, K. (1986) Phytochemistry 25,949. 9. Ahmad, V. U. and Fizza, K. (1987) Liebigs Ann. Chem. 7,643. 10. Chiang, M. T., Bittner, M., Silva, M., Watson, W. H. and Sammes, P. G. (1979) Phytochemistry 18, 2033. 11. Arriaga, F. J. and Borges-Del-Castillo, J. (1985) Magn. Resort. Chem. 23,487.

20,441.

Phytochemistry,Vol. 30, No. 2, pp. 691-693, 1991 Printed in Great Britain.

OOSl-W22/!91 $3.00+0.00 0 1991Pergamon Press plc

SESQUITERPENE ALCOHOLS OF THE COPANE SERIES FROM ESSENTIAL OIL OF OCIMUM AMERICANUM RAM K. UPADHYAY, LAXMI N. MIsRA*t

and GURDIP SINGH

Department of Chemistry, University of Gorakhpur, Gorakhpur, India; *Central Institute of Medicinal and Aromatic Plants. P.B. No. 1, P.O. RSM Nagar, Lucknow 226016, India (Receioed in revised form 6 July 1990)

Key Word Index -0cimum

americanum; Lamiaceae; essential oil; monoterpenoids;

sesquiterpenoids;

copane

derivatives; GC-MS.

Abstract-The volatile oil of Ocimum americanum afforded nine monoterpene hydrocarbons, four oxygenated monoterpenes, 12 sesquiterpene hydrocarbons, 7 sesquiterpene alcohols and a few unidentified trace compounds. Four new alcohols of the uncommon copane series have also been isolated and their structures elucidated by spectroscopic methods and chemical transformations.

INTRODUCTION

Ocimum amerieanum, a herbaceous plant, is found in abundance near cultivated fields and on waste land throughout India. Its leaves, seeds and volatile oil find uses in numerous kinds of food flavour, soaps, cosmetic preparations and also in traditional systems of Indian medicine [l]. It has also been reported that its active principles inhibited in vitro growth of Myobacterium tuberculosis [2] and the aqueous extract showed selective toxicity against Cyperus rotundus [3]. Preliminary investigations on the essential oils of 0. canum have shown that in India it exists in three different chemotypes with methyl cinnamate, camphor and citral as the major constituents [l, 4,5]. However, the essential oil from any chemotype has hitherto not been investigated chemically employing spectroscopic and

1

la

R=H R = AC

3 tAuthor to whom correspondence should be addressed.

Short Reports

chromatographic techniques. In continuation of our screening programme of Indian aromatic flora, we have now investigated this oil revealing the presence of several unknown sesquiterpenoids. RESULTS AND DISCUSSION

Plant material after hydrodistillation gave an oil in 0.7% yield. The oil after GC and GC-MS analysis afforded 44 well-resolved components. Nine were monoterpene hydrocarbons (3 1.6%), four were oxygenated monoterpenes (35.4%), 12 sesquiterpene hydrocarbons (23,44%), seven sesquiterpene alcohols (7.7%) and a few compounds The major unidentified (1.8%). constituents of the oil included a-pinene (8.3%), sabinene (8.0%), limonene (7.8%), camphor (26.7 %) and y-selinene (10.9%). Because camphor, was the major component, leaves had a strong camphoraceous odour and consequently our chemotype belongs to the camphor type. The monoterpene alcohols, borne01 and myrtenol, reinforce the camphoraceous odour but this is long lasting and mild because of the high concentration ( - 31%) of sesquiterpenes and their alcohols. Copane alcohols iinpart a fruity fragrance with spicy undertones, rendering the oil more agreeable to flavouring foods. Most of the constituents were identified by GC R, and mass spectral fragmentation but the major compounds, viz. camphor and borneol were isolated and their ‘HNMR and mass spectra compared with a library established by us. The structures of the new compounds (l-4) were elucidated using spectral methods and chemical transformations. The mass spectrum of 1 showed CM]* at m/z 222 indicating that the compound has the molecular formula C15H260. Its ‘HNMR spectrum did not show any downfield signal below S 1.80, suggesting that it does not contain any double bonds and is a tricyclic sesquiterpene containing a tertiary alcohol. Furthermore, the presence of iso-propyl signals in the ‘H NMR spectrum (0.96, d, J = 7.0 Hz, 6H and 1.80, m, 1H) and the absence of any band for a cyclopropyl ring in the TR spectrum (no bands at 3100-2990 cm- ‘), suggested that the molecule possesses either a copaene or a ylangane skeleton. Because acidic dehydration of 1 yielded a-copaene, whose spectra were comparable to those reported in the literature [6,7-J, it was substantiated that the molecule is copan-3-01. This structure was further supported by singlets at 50.85 for C14 and 61.23 for H-15 in its ‘HNMR spectrum. After acetylation, g yielded la showing an extra signal at 6 2.1 in its IHNMR spectrum. Though we could not assign the stereochemistry at C-3, however, the structure of 1 has, thus, been established as copan-3-01. Similarly, the mass spectrum of 2 showed a [M] + at m/z 220 indicative of an unsaturated alcohol; this was further supported by its IR spectrum which showed bands at 3400 and 1640 cm-l. Its ‘H NMR showed signals at 60.70 and 1.23 for H-14 and H-l 5, respectively, as in case of 1 but, the striking difference was in the chemical shift of the iso-propyl protons. A broad singlet at 64.7 (equivalent to 2H) and a singlet at 61.72 (3H) suggested that 2 is cop-l 1(12)-en-3-01. The mass spectrum of 3 showed a [M] + at m/z 220, but the lH NMR showed a singlet at 60.95 for the methyl at C-14 and two singlets at 1.23 and 1.18 (3H each) indicative of an hydroxyl at C-11. A doublet at 64.87 (2H) clearly suggested that the double bond lies at C-3 [7-J. Therefore, 3 is assigned the structure cop-3( l5)-en- 1 l-01.

The mass spectrum of 4 showed a [MJ’ at m/z 236 indicating that it has a molecular formula of C15H2402. Its ‘H NMR showed a singlet at 60.90 and 1.30 for C-14 and C-15 methyls, respectively, clearly indicating that an hydroxyl is again attached at C-3. A broad doublet at 64.20 (J=6 Hz) suggested that C-12 is also oxidized to hydroxyl and the required double bond lies at A” position. This assignment was further supported by the broad singlet for a vinylic methyl at 6 1.65. These data suggested that 4 is cop- lO( 1 l)-en-3,12-diol.

EXPERIMENTAL

Wild 0. americaurn L. (Syn, 0, canum Sims) was collected from the road side near Gorakhpur (U.P.), India, in October 1987. Airdried aerial portions of the plant (10 kg) were hydrodistilled in batches to obtain 70 ml oil, [d-J3* 0.923 1 [nJ&*’ 1.4900, [a];*“” + 8.75”. ‘HNMR: 80 MHz; ‘%Z’NMR: 20 MHz with TMS as int. standard; chemical shifts are given in 6 units. GC, IR and optical rotation methods were the same as those described previously [S]. GC-MS was carried out using a 30 m OV-101 column prog. from 100 to 200” at 4” min- 1with He (1 ml min- ‘) as carrier gas. Spectra of known constituents were compared with the library established by us and with data reported in ref. [93. All identified components are listed below, 011 (60 ml) was chromatographed over a column of silica gel using petrol (40-60”). The polarity of the eluant was increased using EtOAc (99: 1,97 : 3, 19 : 1 and 9 : 1).The first fr. after further sepn yielded mainly a mixt. of monoterpene hydrocarbons (8 ml). The second fr. after further CC (n-hexane-C,H,) yielded camphor (9 g) while the third fr. gave borne01 (0.7 g). The fourth fr. yielded a complex mixt. of sesquiterpenes. The last fr. after further CC gave 10 frs. The frs when worked-up individually gave 1 (1.6g, TLC, nhexane-EtOAc. 19: 1, R, 0.45); 2 (15 mg, R, 0.40); 3 (35 mg, R, 0.35); 4 (20 mg, R, 0.15). Copan-3-d (1). Crystals, mp 102”, [a];“” +0.62” (CHCI,; c 0.2). IR ~22’~ cm- I: 3400 (OH), 2990-2850, 1460, 1380, 1230, 1100, 1035, 1010. MS m/z (rel. int.): 222 (CM]‘, C,,H,,O) (91,204 [M - H,O] + (78), 189 [204 - Me] ’ (73), 179 CM - iso-propyl] + (4), 175 [189-CH,]+ (lo), 164 [179-Me]’ (24), 161 [175-CH,]+ (63), 109 (SS), 93 (59), 81(77), 59 (78),43 (100). ‘H NMR (CDCl,): 0.85 (s, 3H, H-14), 1.23 (s, 3H, H-15), 0.96(&J= 7.0 Hz, 6H, H-12, H-13),0.56 (d,J=6.0 Hz, lH, H-21, 1.8O(m, lH, H-11). 13CNMR (CHCI,): 69.2 (C-3), 41,4(C-7), 42.3,49.0,39.2,41.0 and 20.4 (C-l, C-2, C-6, C-10 and C-l l), 18.2, 19.0, 19.8 and 22.8 (C-4, C-S, C-8 and C-9), 15.0 (C-12 and C-13), 15.8 and 28.8 (C-14 and C-15). AceryIation of 1. Compound 1 (30 mg) was dissolved in pyridine and Ac,O (SO mg) added; the reaction mixt. was left for 18 hr. After work-up 1s (20 mg} was obtained. Dehydration of 1. Compound 1 (80 mg) was dissolved in MeOH (2 ml) and cone H,SO, (0.05 ml) added. Refluxing of the reaction mixt. was carried out for 3 hr. After work-up and TLC sepns cz-copaene (35 mg) was obtained. Cop-l 1(12)-en-3-01 (2). Viscous mass. IR vEF13 cm- ‘: 3400 (OH), 299&2800,1640 (C=C), 1460,1380,1220.900. MS m/z (rel. int.): 220 (CM]‘, C,,H,,O), (S), 202 [M-H,O]’ (S), 187 [202 -Me] * (lo), 169 (lo), 83 (35), 71(60), 57 (lOO), 43 (95). ‘HNMR (CDCl,): 0.70 (s, 3H, H-14), 1.23 (s, 3H. H-15), 1.72 {s, 3H, H-13), 4.70 (brs, 2H, H-12), 0.75 (d, J=6.0 Hz, lH, H-2). Cop3(15)-en-11-d (3). Viscous mass. IR v,T3 cm- ‘: 3400 (OH), 2990-2800, 1640 (C=C), 1460, 1380, 1210,900. MS, m/z (rel. int.):

220 (CM]+r Cf5Hz40) (2), 202 [M - Hz01 + (41,189 (7), 161 (lo), 121 (18), 71 (48), 57 (65),43 (100). lH NMR (CDCl,): 0.95 (s, 3H, H-14), 1.18 and 1.23 (8, 3H each, H-12 and H-13), 4.87 (d, J = 10 Hz, 2H, H- 15).

Short Reports Cop-lO(ll)-en-3,12-dial(4). Viscous mass showing same tendency to crystallize. IRvscm-‘: 3400 (OH), 2920, 1640, 1370, 1090,lOlO. MS, m/z (reL int.): 236 ([Ml’, C1sHz402) (3), 218 [M - H,O] + (4), 200 [218 - H,O] + (2), 161(54), 109 (65), 95 (78), 45 (lOO), 43 (97), 41 (92). ‘H NMR (CDCI,): 0.90 (s, 3H, H-14) 1.30 (s, 3H, H-15), 1.65 (s, 3H, H-13), 4.20 (d, J=6.0 Hz, 2H, H-12), 0.85 (d, J= 6.0 Hz, lH, H-2). Known compounds. a-Pinene, sabinene, myrcene, B-pinene, car-3-ene, hmonene, a-phellandrene, p-cymene, y-terpinene, epoxytagetone, camphor, cc+gurjunene, iso-humulene, eremophilene, a-humulene, allo-aromadendrene, borneol, y-patchoulene, y-selinene, a-copaene, myrtenol, few unidentified sesquiterpenes and sesquiterpene alcohols. Acknowledgements-We are thankful to Dr R. S. Thakur (Director, CIMAP, Lucknow) and Prof. S. Giri (Head, Department of Chemistry, Gorakhpur University, Gorakhpur) for their encouragement and providing laboratory facilities during the course of this investigation.

693 REFERENCES

1. Anon. (1966) The Wealth of India Vol. 7, pp. 81381. C.S.I.R., New Delhi. 2. Gupta, K. C. and Viswanathan, R. (1956) Antibiot. Chemother. 6, 194. 3. Singh, G. and Pandey, R. M. (1982). J. Agric. Food. Chem. 30, 604. 4. Gulati, B. C., Shawl, A. S., Garg, S. N., Sobti, S. N. and Pushpangdan, P. (1977) Indian Perf: 21,21. 5. Esdorn, I. and Gerda, B. (1949) Pharmazie 4, 70. 6. Kapadia, V. H., Nagsampagi, B. A., Naik, V. G. and Sukh Dev (1965) Tetrahedron 21, 607. 7. Calhghan, R. H. and Morgan, M. S. (1964) J. Org. C/tern. 29, 982. 8. Misra, L. N. and Husain, A. (1987) Planta Med. 53, 379. 9. Swigar, A. A. and Silverstein, R. M. (1981) Monoterpenes. Aldrich, Milwaukee, Wisconsin. 10. Garg, S. N., Misra, L. N. and Agarwal, S. K. (1989) Phytochemistry 28, 634.

Phytochemistry,Vol. 30, No. 2, pp. 693695, 1991 Printedin Great Britain.

0

GUAIANOLIDES

AND OTHER CONSTITUENTS C. ZDERO, F.

Institute

for Organic

Chemistry,

Technical

BOHLMANN

and H. M.

0031 9422/91 $3.00+0.00 1991 PergamonPress plc

FROM STEVIA SPECIES

NIEMEYER*

University of Berlin, D-1000 Berlin 12, F.R.G.; *Facultad Chile, Casilla 653, Santiago, Chile

de Ciencias,

Universidad

de

(Received in revised form 9 July 1990)

Key Word Index-Stevia olides; diterpenes;

eupatoria, S. chamaedrys, S. hyssopifolia; Compositae; ant-labdanes.

sesquiterpene

lactones;

guaian-

Ah&act-The investigation of three Steoia species afforded a large variety of known sesquiterpene lactones as well as one new guaianolide, two known longipinene derivatives, two ent-labdanes and several other common compounds.

INTRODIJCHON

In continuation of our studies on Steuia species [l] we have investigated two species from Chile and one from Mexico. RESULTS AND DISCUSSION

The aerial parts of Steoia eupatoria (Spreng.) Willd. gave, in addition to germacrene D and the longipinene derivatives 9 [Z] and 10 [3], the known guaianolides 5 [4] and 7 [S] as well as 6. The ‘H NMR spectral data of the latter (Table 1) were as expected close to those of 5. The olefinic methyl doublet was replaced by a hydroxymethylene doublet at 6 4.36 which was coupled with a low field triplet at 6 6.78 typical for 4$dihydroxytiglates. Thus, lactone 6 is an isomer of 7 which has a 1(lo)-double bond.

The aerial parts of S. chamaedrys Griseb. crene D, costic acid, its A3 and A4 isomer, reynosin, santamarin, desoxyeupatoriopicrin guaianolides 1[2], 2 [7], 3 [7], 4 [Z] and the

lx.

gave germacostunolide, [6] and the epimers &/h

The aerial parts of S. hyssapijblia Phil. var. hyssopifolia gave no sesquiterpene lactones or longipinene derivatives but in high concentration the em-labdanes 11 and 12 which have been isolated from an Ophryosporus species [8], as well as the more widespread compounds germacrene D, bisabolene, 6,7-dimethoxy-2,2-dimethyl chromene and the p-hydroxyacetophenone derivative 13. These results again show that the chemistry of the genus Steuia is not uniform. However, highly oxygenated guaianolides are quite common. This is also true for the longipinene derivatives. Different diterpenes have also been reported from several species. In a previous invest-