A-norsteroidal ketones in deep sea sediments

Org. Geochem. Vol. 9, No. 2, pp. 101 104, 1986 Printed in Great Britain. All rights reserved

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0146-6380/86 $3,00 + 0 . 0 0 1986 Pergamon Press Ltd

A-norsteroidal ketones in deep sea sediments JAMES McEvoY* and JAMES R. MAXWELL Organic Geochemistry Unit, University of Bristol, School of Chemistry, Cantock's Close, Bristol BS8 ITS, U.K. (Received 23 October 1984; accepted 28 October 1985)

Abstraet--A novel series of C26 to C28 5fl(H)-A-norsteran-3-ones (Ia to c) has been identified in a Late Miocene and two Pliocene sediments from the San Miguel Gap (California continental borderland). Their presence suggests that the bottom waters might have periodically contained sufficient oxygen to allow benthic fauna to survive. Key ,ords: steroid ketones, A-norsteran-3-ones, GC-MS of steroid ketones.

INTRODUCTION

Steroid ketones are known to exist in some marine organisms (see reviews by Schmitz, 1978; Djerassi et al., 1979; Djerassi, 1981) where they are generally present in minor quantities relative to sterols. Recent studies of deep sea sediments have revealed a diverse assemblage of sterols with a wide variety of side chains and nuclei (e.g. Wardroper et al., 1978; Lee et al., 1979; Boon et al., 1979; Brassell et al., 1980; McEvoy et al., 1981; McEvoy and Maxwell, 1983). Correspondingly fewer steroidal ketones have, however, been reported (e.g. Gagosian and Smith, 1979; Brassell et al., 1980; Comet et al., 1981). The steroid ketone distributions of several samples from the San Miguel Gap (Deep Sea Drilling Project Leg 63, Site 467) revealed a wide diversity of nuclei and sidechains and showed many similarities to those of the sterols, particularly with regard to the side chains (McEvoy, 1983). We report here the presence of a series of C26 to C2s 5/~(H)-A-norsteran-3-ones (Ia-c) from a Late Miocene and two Pliocene sediments from this site. EXPERIMENTAL

The solvent extractable lipids of eight sediments from a single hole drilled in the San Miguel Gap (Deep Sea Drilling Project Leg 63, Site 467; 33"50.97'N, 120°45.47'W) have been investigated (McEvoy et al., 1981; McEvoy and Maxwell, 1983). The samples range in age from Quaternary (0.2 Myr BP) to Middle Miocene (c. 16 Myr BP), spanning a depth of about 1 km. The present day water depth is 2146m. The analytical method used to obtain a fraction concentrated in steroid ketones has been described previously (Barnes et al., 1979). Briefly, the lipids obtained by ultrasonication with solvent were divided into acidic and neutral components following saponification. Thin layer chromatography was used *Present address: EAWAG, CH-8600 Dubendorf, Switzerland.

to further separate the neutral components into fractions composed principally of hydrocarbon, ketone and alcohol constitutents. The ketone fraction was analysed by gas chromatography (20mOV-I and SE-52 glass capillary columns) and combined gas chromatography-mass spectrometry (GC-MS; 20 m OV-I fused silica column).

RESULTS AND DISCUSSION

Each ketone fraction from a Quaternary sample (3-3; 0.2 Myr BP; 21 m sub-bottom depth), a Late Pliocene sample (18-5; 2.5 Myr BP; 165 m), an Early Pliocene sample (36-2; 4.5 Myr BP; 333 m) and a Late Miocene sample (54-2; 7 Myr BP; 494 m) contained acyclic, triterpenoidal and steroidal ketones, the latter dominating the fraction. Also present in the Pliocene and Late Miocene sediments was a series of C26-C28 steroidal components having mass spectra with base peak at rn/z 97, a major ion at m / z 217 (Fig. 1) and with molecular ions at m / z 372 (Fig. 2), 386 and 400. The ions at m / z 97, 217, 232 and 276 + 14 n (n = 0, 1, 2 for Ia to c respectively), suggested a pentacyclic A-ring with the keto group at C-3, and the /~(H)-configuration at C-5 by analogy with 14/~(H)-androstan-15-one 0II; Djersaai et al., 1965). Furthermore, the Cz6 component coeluted (GC-MS) with an authentic sample of Ia (supplied by Dr G. Sodano, cf. Minale and Sodano, 1974) and the mass spectra compared favourably. The C26 component has also been tentatively assigned in an Italian black shale (Van Graas, 1982). The standard contained minor amounts of a C27 and a C28 homologue; these coeluted with the sedimentary compounds, indicating that the latter are Ib and Ic respectively. A minor C2s component (X in Fig. 1), eluting just before 24-ethyl5/~(H)-A-norsteran-3-one (Ic) is tentatively assigned as Id from its spectrum and comparison with the elution positions of IIc and lid and their corresponding saturated alcohols (McEvoy and Maxwell, 1983). Within the ketones, the 5/~(H) isomer is the more stable (Biellmann et al., 1960) and the 5~(H) isomer 101

02

JAMES McEvov and JAMES R. MAXWELL

C28

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I

Car

!l m/z 217

RIC X •

1400

I

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'

1600

~

'

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1800

Scan No.

m/z

Fig. I. Part of the reconstructed ion current chromatogram (RIC) and of mass chromatograms of 97 and of 217 for a ketone fraction from sediment sample 54-2 (Late Miocene). Temperature programme, 50-280°C at 4°C min-I; OV-I, fused silica column (20 m × 0.25 mm i.d.); He carrier.

m/z

97

217

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372

~~

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199

232 •

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m/z Fig. 2. Mass spectrum of A-nor-5/~(H)-cholestan-3-one (la; scan 1464 in Fig. 1).

,I

I

II -.

A-norsteroidal ketones in deep sea sediments readily converts to it upon standing (Sodano, personal communication), presumably via enolisation at C-3. Since each solvent extract was saponified and chromatographed on silica, we are unable to prove conclusively the configuration at C-5 of the ketones when present in the sediment. The fact that the A-nor-steranes in the two deepest sediments (Middle Miocene, 97-2 and 110-3, c. l km below sediment/ water interface) have been shown previously to have the 5,8(H) configuration (McEvoy and Maxwell, 1983) implies, however, that the ketones do indeed occur in the sediments with this configuration (see below).

I

R

11

103

consistently high values of organic carbon observed throughout Site 467 (e.g. Gilbert and Summerhayes, 1981) testify that the bottom waters were generally oxygen-poor. It is possible, however, that the presence of the A-nor ketones in the Pliocene and Late Miocene sediments, taken with their absence in the Quaternary sample, could indicate that the bottom waters in the Piiocene and Late Miocene periodically contained sufficient oxygen to allow benthic fauna to survive (cf. Van Graas et al., 1982). If the A-nor ketones are indeed related to 3,8hydroxymethyI-A-nor sterols (IVa-c), the latter might be expected to occur in the sediments still containing

R

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~

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To our knowledge, the only biological A-nor compounds are the 3fl-hydroxymethyl-A-nor-5~ (H) sterols (IVa-c) found in several species of sponge (Minale and Sodano, 1974; Kanazawa et al., 1979; Bohlin et al., 1981; Djerassi, 1981). Indeed, labelling experiments (de Rosa et al., 1975 and 1976) have shown that Axinella verrucosa can transform dietary cholesterol (IIa) into IVa. On this basis, Van Graas et al. (1982) have suggested that sedimentary A-norsteranes (Va-c) are indicators of an input from certain types of sponges with the 3fl-hydroxymethyl group being removed by microbial action at an early stage of diagenesis. On this basis, the ketones could also arise from sponges. Furthermore, abundant sponge spicules are reported in sediments at Site 467, including cores 18, 36 and 54 (Shipboard Scientific Party--Site 467, 1981). On the other hand, the

sterols (18-5 and 36-2); neither these compounds nor sterols with the same carbon skeleton as the ketones have, however, been recognised so far. In the deeper, Middle Miocene sediments (97-2 and 110-3), the C26 to C28 5fl(H)-A-norsteranes co-occur with C26 to C2s A-nor-sterenes (position of nuclear double bond uncertain). The absence of the corresponding ketones in these two deeper sediments, taken with the appearance of the hydrocarbons, suggests a diagenetic relationship between them, in that the hydrocarbons may have arisen from the reduction of the ketones. Other classes of sedimentary A-nor-steroids have been tentatively assigned, including diasterenes (Van Graas et aL, 1982) and ring-C aromatic hydrocarbons (Brassell, 1984). It is clear, therefore, that the members of the A-nor steroid family of compounds, like the "regular"

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JAMES McEvoY and JAMES R. MAXWELL

steroids, undergo complex diagenetic p a t h w a y s ( c f Mackenzie et al., 1982). Acknowledgements--We thank the Natural Environment Research Council (GR3/2951 and GR3/3758) for GC-MS facilities and for a Studentship (J.M.). We are also grateful to Dr G. Sodano for a mixture containing la-Ic, to Mrs A. P. Gowar for technical assistance, and to Dr S. C. Brassell and Mr Torren Peakman for valuable discussions. REFERENCES

Barnes P. J., Brassell S. C., Comet P. A., Eglinton G., McEvoy J,, Maxwell J. R., Wardroper A. M. K. and Volkrnan J. K. (1979) Preliminary lipid analyses of Core Sections 18, 24 and 30 from Hole 402A. In Initial Reports o f the Deep Sea Drilling Project (Edited by Montadert L. et al.), Vol. 48, pp. 965-976. U.S. Government Printing Office, Washington. Biellman J. F., Francetie D. and Ourisson G. (1960) Effects conformationnels sur l'6quilibre cis-trans D'~-hydrindanones. Tett. Lett. 18, 4-9. Bohlin L., Sjostrand U., Djerassi C. and Sullivan B. W. (1981) Minor and trace sterols in marine invertebrates. Part 20. 3~-hydroxymethyl-A-nor-patinosterol and 3@ hydroxymethyl-A-nor-dinosterol. Two new sterols with modified nucleus and side-chain from the sponge Teichaxinella morchella. J. Chem. Soc. Perkin I, pp. 1023-1028. Boon J. J., Rijpstra W. I. C., De Lange F., De Leeuw J. W., Yoshioka M. and Shimizu Y. (1979) The Black Sea sterol - - A molecular fossil for dinoflagellate blooms. Nature 277, 125-127. Brassell S. C., Comet P. A., Eglinton G., Isaacson P. J., McEvoy J., Maxwell J. R., Thomson I. D., Tibbetts P. J. C. and Volkman J. K. (1980) Preliminary lipid analysis of Sections 440A-7-6, 440B-3-5, 440B-8-4, 440B-68-2 and 436-11-4 from DSDP Legs 56 and 57. In Initial Reports o f the Deep Sea Drilling Project (Edited by yon Huene R. et al.), Vol. 57, pp. 1367-1390, U.S. Government Printing Office, Washington. Comet P. A., McEvoy J., Brassell S. C., Eglinton G., Maxwell J. R. and Thomson I. D. (1981) Lipids of an Upper Albian limestone, Section 465A-38-3. In Initial Reports o f the Deep Sea Drilling Project (Edited by Thiede J. et al.), Vol. 62, pp. 923-937. U.S. Government Printing Office, Washington. de Rosa M., Minale L. and Sodano G. (1975) Metabolism in Porifera IV. Biosynthesis of the 3fl-hydroxymethyl-Anor-5~-steranes from cholesterol by Axinella verrucosa. Experientia 31,408-410. de Rosa M., Minale L. and Sodano G. (1976) Metabolism in Porifera VI. Role of the 5,6 double bond and the fate of the C-4 of cholesterol during the conversion into 3fl-hydroxymethyl-A-nor-5~-steranes in the sponge ,4xihello verrucosa. Experientia 32, 1112-I 113, Djerassi C. (1981) Recent studies in the marine sterol field. Pure Appl. Chem. 53, 873-890, Djerassi C., Von Mutzenbecher G., Fajkos J., Williams

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