Indian Journal of Chemistry Vol. 42B, May 2003, pp. I un- I 1 89

Note

A minor pseudoguaianolide from the aerial parts of Parthenium hysterophorus L.

Padma Acharyya & Nabin C Barua*

Organic Chemistry Division (Natural Products Chemistry), Regional Research Laboratory, Jorhat 785006, Assam, India

Fax: (+9 1 )-0376-2370 0 1 1

Received 29 January 2002; accepted (reviseu') 16 September 2002

Chemical investigation of the aerial parts of Parthenium hy�­terophorus L. (Asteraceae) has yielded a new pseudoguaianolide in addition to several previously reported compounds.

The cosmopolitan weed, Parthenium hysteropho­

ntS L. was the cause of a serious outbreak of al lergic eczematous dermatitis in parts of India, e.g. , Poona, where it was introduced in 1 956 from the Americas. I This plant is also reported to cause l ive-stock poison­ing to domestic animal s2. 3 . The allergenic compounds in this weed are the pseudoguaianol ides, parthenin and ambrosin4 which are also found in other genera of the Compositae such as Iva, Ambrosia, and Hymeno­

des.8. In addition to these, some minor pseudoguaia­nol ides have also been isolated from this plant9. 1 5 . This aggressive weed is also abundantly avai lable in the Brahmaputra valley and is known to cause l ive· stock poisoning. In continuation of our interest on the chemical investigation of the medicinal plants of southeastern sub-Himalayan region l 6. 1 7, we undertook the chemical investigation of Parthen ium hysteropho­

rus and isolated a new pseudoguaianolide 2. Our plant material came from the Bhatiapar area of Sibsagar District, Assam, India.

Results and Discussion

The residue obtained after evaporation of the hot chloroform extract of the aerial parts of Parthenium

hysterophorus was subjected to chromatography on a silica gel column, followed by Preparative Layer Chromatography (PLC) to yield compounds 1 and 2, of which compound 2 is reported for the first time.

The mass spectrum of 2 gave a molecular ion peak at mlz 337(M+ + 1 ) indicating a molecular weight of 336. By combined analysis of MS, NMR and IR data, its molecular formula was suggested as C 17H2007. The IR spectrum of 2 indicated the presence of hydroxyl

2 3 0

group (3400 cm· I ), an a-methylene-y-butyrolactone moiety ( 1 765 cm· I ), a cyclopentenone moiety ( 1 722 cm· I ), and an ester grouping ( 1 740 cm· I ) . The IH NMR spectrum of 2 showed a three proton singlet at 8 2.08 indicating the presence of an acetoxy group in it. A pair of doublets with one proton each at 8 5 .62 and 6.26 (1=2.7 Hz) was assigned to the exomethylene protons conjugated with a carbonyl . The typical dou­b let integrating to one proton at 8 5 .08 (J= 8 Hz) and a singlet integrating to three protons at 8 1 .27 for a methyl group suggested the pseudoguaianol ide struc­ture for this compound 1 8 . A pair of doublets integrat­ing to one proton each at 8 7 .7 1 and 6.27 (1=6 Hz) indicated the presence of a a,B-unsaturated pentenone system. Absence of the characteristic C lo-methyl dou­bietl 9 at 8 1 .0 and the presence of three proton singiet for the acetoxy group at 8 2.08 and a two proton dou­blet at 8 4. 1 4 ( J=6.2 Hz) showed the preseilce of a C l4'acetoxy group in the molecule. A one proton dou­blet of triplet at 8 3 .5 (1= 8.4 and 4.0 Hz) indicated the presence of a hydroxyl group at C8.

The other hydroxyl as demanded by its molecular formula and supported by its IR has been established to be at C I as the characteristic singlet of the C I pro­ton was absent in its NMR spectrum. Hydrogenation of 2 on Pd/C catalyst gave a tetrahydro derivative 3, which indicated that the molecule contains two ole­finic double bonds. Based on the above information structure 2 has been assigned to this compound.

Experimental Section General. Melting point was determined with Buchi

540 melting point apparatus and is uncorrected. IR spectra were recorded on a Perkin-Elmer 236 gratting infrared spectrometer; NMR spectra on a Brucker DPX 3000 spectrometer in CDCI3 solutions using TMS as the internal standard (chemical shifts in 8, ppm); and mass spectra on a Brucker HPLC-MS

1 1 88 INDIAN J. CHEM., SEC B, MAY 2003

equipment at 70 eV. The optical activIty measure­ments were done on a Perkin-Elmer polarimeter model 343. Silica gel G was used for TLC.

Plant material. The above ground part of Parthe­

nium hysterophorus Linn. (Compositae) was collected from the Bhatiapar area of Sibsagar District, Assam, India in May 1 999. A voucher speciman has been de­posited at the Herbarium of the Plant Science and Ecology Division of the Regional Research Labora­tory, Jorhat, Assam, India.

Aerial parts of Parthenium hysterophorus Linn. (2 Kg) were extracted with chloroform in a Soxhlet apparatus until the extract became colourless. The extract was evaporated in a rotavapour under reduced pressure to yield a gummy residue (40.06 g), which was dissolved in 100 mL of 10% aq. methanol and left at room temperature over night. The extract was filtered and the filtrate was washed with hexane (3xI00mL) until the washings were almost colourless. The aqueous methanol extract was concentrated to a volume of about 70 mL and then extracted with chloroform (3 x 100 mL) until the washings were almost colourless. The combined extracts were dried over anhydrous Na2S04 and evaporated under reduced pressure to yield a gummy residue ( 14.5g) which was chromatographed over column of silica gel 60- 1 20 mesh (250g); packed in hexane and then 150 mL fractions were collected in the following order: Fr. l -16 ( 1 : 1 , EtOAc : Hexane); Fr. 1 7-23 (2: 1 , EtOAc : Hexane); Fr. 24-35(4: 1 , EtOAc : Hexane);Fr. 36-63, (6: 1 , EtOAc : Hexane). Fractions 24-27 showed a single spot on TLC. (EtOAc : Hexane, 2: 1 ) and were combined. Evaporation of this combined fraction gave a residue ( 100 mg) as a gum which has been found to be homogeneous on TLC. However, 300 MHz IH NMR spectrum revealed it to be a 2: 1 mixture of two closely identical compounds. Separation of these two compounds was achieved by preparative TLC. using 2% methanol in chloroform as solvent system and running the plate 14 times whereupon it gave compound 1 (35 mg) and compound 2 (20 mg).

Compound 2, a colourless gum, [a]25D -13 .3° (MeOH, c 0.6); IR(CHCh): 3400, 2900, 1765, 1740, 1722, 1660, 1450, 1415 , 1 375, 1280, 1 250, 1 175 and 1 130 cm· l ; MS: mlz 337(M++l ), 292, 278, 261 , 243, 233, 215, 200, 1 88, 177, 1 56, 146, 132, etc. ; IH NMR: 8 7.7 1 (d, J = 6 Hz, I H, H-2), 6.27 (d, J = 6 Hz, IH, H-13b), 6.26 (d, J = 2 .7 Hz, I H, H-3), 5 .62 (d, J = 2.2 Hz, I H, H- 1 3a), 5 .08 (d, J = 8Hz, I H, H-6), 4. 14 (d, J = 7 .3 Hz, I H, H-6), 4. 1 5 (d, J = 6 .2 Hz, 2H, H-14), 3.5 (dt, J = 8.4 and 4.0 Hz, I H, H-8), 2.5 (m, 2H,

H-9), 2.08 (s, 3H, OAc), 1 .87 (t, J = 5 Hz, I H, H-7), 1 .27 (s, 3H, Me); \3C NMR (CDCh, 75.4 MHz): 0 8 1 .09 (C- l ), 1 23.9 (C-2), 1 29.6 (C-3), 208.01 (C-4), 42.6(C-5), 76.49(C-6), 44. 1 (C-7), 77 .5 1 (C-8), 30.5(C-9), 42.04(C- I O) , 1 38.7(C-l 1 ), 168.7(C- 1 2), 129.6(C-13), 8 1 .6(C- 14) , 1 9.02(C- 15), 169.7 (Acetyl C=O), 12 . 1 (acetyl CH3) . Anal. Calcd for C17H2007: C, 60.7 1 ; H, 5 .99. Found: C, 60.63, H 5.82.

Hydrogenation 0/2. Compound 2 ( 1 5 mg) in abso­lute alcohol ( 1 5 mL) was hydrogenated over 10% pal­ladium charcoal ( 1 0 mg) at 50 Psi pressure of hydro­gen for 6 hr. The reaction mixture was filtered and the catalyst was washed thoroughly with ethanol, distilled off the filtrate under reduced pressure to yield a resi­due, which was purified by preparative TLC (7% methanol in chloroform) to furnish 3 ( l0 mg) as a crystalline solid, mp 1 85°C; [a] � + 1 3°(MeOH, c0.49); IR (CHCh): 3400, 2995, 1740, 1 250, 1050 cm' I ; MS: m/z 340 (M+), 297, 1 89, 279, 1 79, 261 , 174, 9 1 , 83.77; IH NMR: 8 1 .2 (s, 3H, CH3), 1 .7(d, J=7.2 Hz, . 3H, CH3), 2.08 (s, 3H, OAc), 1 .9-2.5 (m, 8H), 3 .0 (br, 2H, D20 exchangeable), 4.05 (dd, J = 7.07 & 14.8 Hz), 4.28 (dd, J = 4.9 & 1 1 .3 Hz), 5.2 (d, J = 2 Hz).

Acknowledgement

Authors thank Dr M J Bordoloi for recording the 300 MHz NMR spectra and Director, RRL, Jorhat for providing facilities for this work.

References I Lonkar A, Mitchell J & Calnan C D, Trans St John Hosp

Derm Soc, 60, 1974, 43. 2 Narsimhan T R, Ananth M, Swamy M N, Babu M R, Mangla

A & Rao P V S, Experientia, 33, 1971, 1 358. 3 Das K & Das B, Indian J Heterocyclic Chem, 7, 1977, 1 63. 4 Rodriguez E, Dillon M, Mabry T J, Towers G H N &

Mitchell J C, Experientia, 32, 1976, 236. 5 Rodriguez E, Yoshioka H & Mebry T J, Phytochemistry, 1 0,

1976, 1 145. 6 Herz W, Recent Advances in Phytochemistry, Vol I , edited by

T J Mebry, R E Alston & V C Runeckles, (Appleton-Century Crot, New York), 1968, 229.

7 Herz W, in Chemistry in Botanical Classification, Noble symposium 25, (edited by G Bendz & J Santesson, (Aca­demic Press, New York), 1973.

8 Toribro F P & Geissman T A, Phytochemistry, 7, 1968, 1 623.

9 Herz W, Watanabe H, Miyazaki M & Kishida Y, J Am Chem Soc, 84, 1962, 260 1 .

1 0 Das K & Das B , Indian J Heterocycl Chem, 7, 1977, 1 63 . I I Pic man A K, Towers G H N & Rao P V S, Phytochemistry,

1 9, 1980, 2206. 1 2 Sethi V K, Kaul S K, Taneja S C & Dhar K L, Phytochemis·

try, 26, 1987, 3559.

NOTES 1 1 89

13 Talwar K K & Kalsi P S, Phytochemistry, 28, 1989, 109 1 . 1 4 Kalsi P S , Mittal V, Singh I P & Chhabra B R , Fitotherapia,

66, 1995, 1 9 1 . 1 5 Bhullar M K , Kalsi P S & Chhabra B R , Fitoterapia,

LXXVIII, 1997, 9 1 . 16 Bordoloi M J, Barua N C , Mohan S, Dutta S C , Mathur R K,

Ghosh, A C & Recklewska U, Tetrahedron Lett, 37 (37),

1996, 679 1 . 17 Bordoloi M J , Barua N C , Mohan S, Dutta S C,. Mathur R K

& Ghosh A C, Phytochemistry, 45, 1997, 9. 1 8 Chhabra B R, Kohli J C & Dhillon R S, Phytochemistry, 52,

1999, 1 33 1 . 1 9 Romo de Vivar A , Bratoeff E A & Rios T, J Org Chem, 3 1 ,

1966, 673.