Akywbemivrry, Vol. 25. No. 8. pp. 189!3-1902. 1986. 003 I -5w2/%6 $3.00 + 0.00 Rioti in Grcar Britain. Ferpmoa Joumah Ltd.

OX0 ACIDS AND BRANCHED FA’ITY ACID ESTERS FROM RHIZOMES OF COSTUS SPECIOSUS

MADAN hi. GUFTA, RAM K. VERMA and ANAND AKHIU

Central Institute of Mcdkinal and Aromatic Plants, Lucknow-226016. India

(Receiurd II Drcemtw 1985)

Key Word Iadcx-Cosru~ sp~~iosuq Cas(aapc; rhizomcq tctradazyl 13mcthylpcntadccmoxtc; tetradql I I-methyltrkkanoxt~ M-oxoWicusxnoic rcid, M-oxoheptacusan oic acid; U-oXooc~Oic acid; 5a-sligluxxt- 9( I 1)-a-3/M; diosgenin; sitostcrol; triacontxnol; triacontanoic acid.

Abtract-Five new compounds, isolated from the rhizomes of Co;Ftus speciosus have been characterized as tetradecyl Wnethylpentadecanoate, tetradecyl 1 I-methyltridecanoatc, M-oxot ricosanoic acid, 14-oxoheptacosanoic acid and 1 S- oxo-octacosanoic acid by spectral and chemical studies. Triacontanol, k-stigmast-9( 1 lm-3/3-ol, triacontanoic acid, sitosterol and diosgenin have also been isolated and identified.

INTRODUCTION

Costus speciosus is a rich source of diosgenin which is used for the synthesis of steroidal drugs. The compound has been reportal to occur in all parts of this plant in varying percentages [l-4]. During a large scak isolation of diosgenin from the rhizomes of the plant it was of interest to investigate the compounds from the hexane solubk fraction since they have not been examined.

RESULTS AND DISCUSSION

Ten compounds (l-10) were isolated by silica gel chromatography. followed by prep. TLC of the n-hexane extract of the rhizomes of C. speciosus.

Compound 1, mp -2”. had IR absorption bands at 1730 (ester CO) and 730,720 cm- ’ (long chain). The mass spectrum displayed an [M] + at m/z 452, which established the mokcular formula as CJOH6001. The ‘HNMR spectrum of 1 displayed a tripkt at 60.88 and adoubkt at 60.80 for two terminal and one branched methyl groups, respectively. A methylene group adjacent to the CO function was seen as a tripkt at 62.28. Another triplet was observed at 64.00 for -CH-O-CO- protons. Alkaline hydrolysis of 1 afforded an alcohol. mp 41-43”, identaied as tctradecanol (IR, mass spectrometry, lit. mp X-39.5” [S]) and an acid, mp 65-66”. which had an [Ml+ at m/z 256 (C16H3202) and showed IR bands for acid [6] at 1700,3300-2500and 920 cm- ‘. The mass spectrum of the acid had a /?-fission ion at m/z 60 which is characteristic of a terminal carboxyl group. The presence of an [M - 153 + ion at m/z 241 showed the branched chain nature of this acid [7]. The base pa& at m/z 57 favoured the position of branching at C-13. In the ‘H NMR spectrum the terminal methyl group was observed as a triplet at 60.88 and the branched methyl as a doublet at 60.80. The methykne group adjacent to the carboxylic group was seen as a triplet at 62.28. These data suggested the structure of the acid as 13-methylpentadecanoic acid.

On the basis of its hydrolysis products, 1 should therefore be tetradecyl 13-methylpentadecanoate. The mass spectral fragmentation was consistent with the proposed structure. The ions at m/z 255,241,239,213,197

and at m/z 256 and 1% were due to a- and /3-fissions, respectively, of the ester group. The base peak at m/z 57 again supported branching at C-13 in the acid moiety of this ester.

Compound 2, mp 58-61”. posses& IR bands at 1725 (ester CO), 725 and 720 cm- ’ (long chain). The [M]’ at m/z 424 led lo the mokcular formula of CzeH,eOI. The ‘H NMR spectrum of 2 was similar to that of 1. Alkaline hydrolysis of 2 afforded tetradecanol and an acid, mp 6365”. [M]’ m/z 228 (C,.H2s0z), v, 1700.3300-2500 and920cm-‘. Similar lo the acid obtained from 1, it had an [M - IS] l fragment indicating a methyl group as a substituent. The base peak at m/z 57 supported the position of branching at C-l 1. The ‘H NMR spectrum of this acid was similar to that of the acid from 1 and it was identified as 1 I-methyltridecanok acid.

Therefore, on the basis of its hydrolysis products. 2 was identified as tetradecyl 1 I-methyltridecanoate. The mass spectral fragmentation of 2 was consistent with the proposed structure. Thus, a-fission ions were observed at m/z 241,227,213,211, 197 and 183 whik the ions at m/z 256 and 168 were due 10 /3&sion. The base peak at m/z 57 indicated the presence of a methyl group at C-l 1 of the acid moiety.

Compound 6. mp 74-77”, gave a positive 2,4dinitro- phenylhydrazine test (DNP)and had IR absorption bands

m/x 57

Me-CH>-CH (CHx)u--Me

1

M. M. GUFTA n cd.

m/z 227

m/r 211

7-l m/r’83 7 m/z 168 7

2

for a COOH group at 3400-2500 (br), 1700, 1270 and 92Ocn~‘andforacarbonylfunctionat 1720cm-‘.The bands at 725 and 715cm-’ suggested its long chain nature. The [Ml’ at m/z 368 suggested tbe mokcular formula CzJHuOJ. The ion at m/z 60 indicated the presence of a terminal COOH group in the compound. The position of the carbonyl group at C- 14 was obtained from the prominent a- and /I-fission ions (involving McLatTerty rearrangement [8]) at m/z 241,213, 155 and 127 and at m/z 256, 198 and 112, respectively. A doubk rearrangement ion at m/z 58 indicated tbe presence of v H atoms in both the alkyl fragments. The presence of an [M + 13’ ion showed the unsymmetrical nature of tbe ketone [9, lo] whereas the straight chain nature was supported by the absence of an [M - 13’ ion. The ‘HNMR spectrum of Qshowed a tripkt for a terminal methyl group at 60.88 (J = 6 I-Ix) and another triplet, integrated for six protons was at 62.25 (J = 6Hx) for three methykne groups adjacent to carbonyl and carboxylic acid functions.

Reduction of 6 with sodium borohydride yielded a hydroxy acid, mp 80”, which lacked CO absorption but showed a band for hydroxyl at 3430 cm- ’ . The [M] + ion was not observed, the mokcuk losing water to give an ion at m/z 352. The a-fission ions corresponding to the C-14 hydroxyl group were observed at m/z 243,213, 157 and 127. The above data led us to characterize 6 as 14 oxotricosanoic acid.

Compound 7, rnp 80-82”. showed a positive 2.4DNP test and its IR and H NMR spectra were similar to those of 6. An [M] ’ ion at m/z 424 suggested the molecular formula Cz7HSz0,. The CO group was located at C-14 since the a-fission ions were seen at m/z 241,213,211 and the /I-fission ions at m/z 226 and 256. Reduction of 7 with

m/r 60

f

m/r 45

Me-_(CH,h C%H

sodium borohydride yielded a hydroxy acid, mp 8485”. m/z 408 CM - HzO]‘. The a-fission ions at m/z 243,213 and 183 were in accordance with the hydroxyl group at C- 14. The data described above were fully consistent with the structure of 7 as 14-oxobeptacosanoic acid.

Compound S, mp 83-85”, also gave a positive 2.4DNP test and its ‘H NMR and IR spectra were similar to those of 6 and 7. An [Ml’ ion at m/z 438 in its mass spectrum established the mokcular formula as CzeHS40,. The position of the CO group was establisbed at C-14 since prominent a-fission ions were observed at m/z 241, 2.25, 213 and 197, and /Lfission ions at m/z 256,240, 198 and 182 The presence of an [M + l] + ion and the absence of one at [M - 151’ suggested its unsymmetrical and un- branched nature. Reduction of 8 with sodium borohyd- ride yielded a hydroxy acid, mp 86”, which showed an [M - HzO]+ ion at m/z 422 The a-fission ions at mfz 243, 227, 213 and 197 deduced the position of the hydroxyl group at C-14. Thus, g was characterized as 14oxo-octa- cosanoic acid.

Compound 3, mp 8486”. was characterized as tri- acontanol by IR, NMR. mass spectrometry and com- parison with an authentic sampk. Compound 4, mp 132”. was identified as 5 a-stigmastd(ll)-en-3fl-ol by direct comparison with authentic material, isolated by us pre- viously from the roots of this plant [ 111. Compound !I, mp 92-93”, was identified as triacontanoic acid (IR, NMR, mass spectrum) by comparison with an authentic sampk. Compounds 9 and 10, mps 135-136” and 200-202”. were identified as sitosterol and diosgenin. respectively, by direct comparison with authentic sampks.

. * .

0x0 acids occur in milk, fat, lipid, oil, epicuticular wax, latex and rhizomes. Most natural straight chain acids,

7

6

1902 M. M. GUPTA et Irl.

Rufrrion of 8. Cmpound 8 (9 mg) WM dholvcd in McOH (5ml)~NIBH4(5ms)ddcdIrdurllyradrtirradfor4hr. After uslul work up 5 m8 of a hydroxy acid were isolated, mp 8w (MelCOj IRv,cm - ‘: 3450,291q 2840, 3400-2500, 1700. 14% 1380. 128Q 11% 1070,944 7% 715. MS m/z (reL iot): 422 [M -H1O]+ (5). 243 (8j 227 (lo), 213 (6). 197 (12j 60 (6Oj 57 (85j 45 (2). 43 (100).

Sitarraol(9j Elutal in tbc C& fnxctions X0-354 40 m& mp 135-136” (MeOH). ldentilied by IR, MS. mmp. co-TLC.

Diozgcnin (10). Obthcd from the C&,-CHCl, (17:3) frae tiona, 90 m8, mp 200-202” (MeOH j Idcntitial by mmp.ceTLC, MS. IR.

Achnowkd~--We arc grateful to Dr. Akhtar Hush, Diraxor, for hir kan interest duriq tbc count of this work.

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