Phytochemrstry, Vol 27, No 11,pp 3625-3626, 1988 0031 9422/88 $300+000 PrInted ,n Great Bntam 0 1988 zyxwvutsrqponmlkjihgfed Pergamon Press plc zyxwvutsrq PHENANTHRENE AND STILBENES FROM zyxwvutsrqponmlkjihgfedcbaZYXWVUT PTEROLOBIUM HEXAPETALLUM R JAGDISH KUMAR, D. JYOSTNA, G. L. DAVID KRUPADANAM and G. SRIMANNARAYANA* Department of Chemistry, Osmama Umverslty, Hyderabad 500007, India (Recerued 26 August 1987) Key Word Index-Pterolobrum hexapetalhm, Legummosae, phenanthrene, trl-O-methyl resveratrol, methyl tn-O- methyl gallate, pterostllbene, resveratrol, methyl gallate. Abstract-From the stems of Pterolobmm hexapetallum phenanthrene, tn-O-methyl resveratrol, methyl tn-O-methyl gallate, pterostllbene, resveratrol, methyl gallate were Isolated The natural occurrence of phenanthrene has not previously been reported The structures were determined by analytical and spectroscopic methods INTRODUCTION Pterolobwn hexapetallum (Roth) (sub family Caesalpma- ceae) has to our knowledge, not been subjected to sys- tematic chemical investlgatlons. This study shows that the stems contam, phenanthrene (I), whose natural occur- rence has not previously been reported, together with the known substances, tn-0-methylresveratrol(2), methyl tri- O-methyl gallate (3), pterostilbene (4), resveratrol(5) and methyl gallate (6). Tri-O-methyl resveratrol and methyl tri-O-methyl gallate were recently reported from Virola elongata and Heracleus canescens respectively for the first time [l, 23. RESULTS AND DISCUSSION Compound 1 IS a colourless crystalline solid (M + 178). The UV spectrum showed only aromatic absorption and only C=C, C-C and C-H absorptions were seen in the IR spectrum The ‘HNMR spectrum (500 MHz) showed peaks only m the aromatic region. Compound 1 was Identified as phenanthrene by mp and comparison with published spectral data [3-51. In the 500 MHz ‘H NMR spectrum of phenanthrene, now recorded, all the proton signals are clearly resolved and assigned. Whereas the 90 MHz spectrum reported earlier [S] revealed only two unresolved multiplets. Compounds 2-6 were identified as t&O-methyl re- sveratrol [ 11, methyl tn-O-methyl gallate [2], pterostil- bene [6], resveratrol[7,8] and methyl gallate [9] respect- ively, by comparison of analytical and spectral data with the reported values. Phenanthrene may be conceived to have been derived blogenetically from the correspondmg unsubstltuted stil- bene by ring closure [lo]. It 1s therefore significant to note the occurrence of stllbenes 2, 4 and 5 along with phenanthrene m the same plant. EXPERIMENTAL dissolved m mmlmum amount of MeOH (500 ml) and adsorbed onto the already extracted plant material (500 g). The adsorbed plant material was dried and re-extracted successively with petrol (bp 60-80”, 2 I), CHCI, (2 I) and EtOAc (2 I) m a Soxhlet extractor. The extracts were concentrated to yield the followmg semi-sohds petrol extract (3 g), CHCI, extract (10 g) and EtOAc extract (I6 g) The petrol and CHCI, extracts were combined due to their similar behavlour on TLC The combmed extract (I3 g) was then subjected to CC over silica gel (1 IO g, 200 mesh). Fractions of 50ml each were collected by elutmg successively with C,H,-EtOAc (I9 I) Fraction I did not yield any product Fractions 2 and 3 afforded phenanthrene (1,45 mg) mp 99” ht. mp loo” [3], fractions 5-8 afforded tn-O-methyl resveratrol (2, 60mg) mp 57” ht. mp 5657” [I], fractions 11-13 afforded methyl tn-O-methyl gallate (3, I g) mp 80” ht mp 80” [2] and fractions 15-18 afforded pterostdbene (4,100 mg) mp 88”, lit mp 88-89” [6] The EtOAc extract (16 g) was subJected to CC over silica gel (135 g, 200 mesh) Fractions of 50 ml each were collected by elutmg with C,H,-EtOAc (7 3) Fraction 1 and 2 did not yield any product Fractions 3-5 gave a pale yellow solid which crystalhzed from dry Me,CO as pale yellow needles of res- veratrol (5, 120 mg) mp 248” ht mp 248” [S] and subsequent fractions 7-20 gave methylgallate (6, 6 g) mp 202”, ht mp 202” [3]. The spectral data (IR, UV, NMR and mass) of ld are in agreement with those reported for these compounds m literature zyxwvutsrqpo Cl-91 Phenanthrene (1) UV it::” nm 210,220,250,274 (sh), 280(sh), 293, 330 (sh), IR v!c,,f: cm-’ 3040, 1600, 1520, 1500, 1445, 1425, 1300,1240,810,730, ‘H NMR (500 MHz, CDCI,) 67.63 (2H, t, J =7 3 Hz, 7.3 Hz, H-2, H-7), 7 68 (2H, t, J= 7.6 Hz, 8 2 Hz, H-3, H-6), 7 77 (2H, s, H-9, H-lo), 7 92 (2H, d, .I= 7 8 Hz, H-l, H-8) and 8.72 (2H, d, 5=8 2 Hz, H-4, H-5), ‘%NMR (CDCI,) 6 122.96 (d, C-4, C-5), 126 79 (d, C-2, C-3, C-6, C-7), 127 18 (d, C-9, C-lo), 128 81 (d,C-l,C-8), 130 69(s, C-9a,C-IOa), 132 44(s, C-4a, C-5a), MS 70 eV m/z (rel mt ) 179 (60) [M + l]‘, 178 (100) [Ml+, 177 (36), 176 (58), 152 (38), 151 (35), 150 (20), 139 (5), 126 (5), 89 (35), 76 (40) The air-dned and powdered stems of P hexapetallum (4 kg) obtained from the forests of Mannanoor, Andhra Pradesh, India Acknow ledgements- O ne of the authors (RJK) thanks the CSIR, were extracted with MeOH (121) and the extract concentrated New Delhi for the award of JRF. We thank the Chief Conser- under red pres to give a black gummy residue (60 g) which was vator of Forests and Mr K Jaganmohan Rao (Conservator of 3625