Phytochemical Study Conyza Sophiaefolia. Antiinflammatory Activity

Abstract

From the aerial parts of Conyza sophiaefolia a new alicyclic furan diterpene was isolated and characterized as an E-isomer in C₆ of centipedic acid. In addition, the new clerodane type diterpene 12-epi-bacchotricuneatin A as well as two known related diterpenoids were identified. The flavone apigenine was also isolated. Structures were determined on the basis of spectroscopic evidence.

Introduction

The genus Conyza comprises about 50 species, which are mainly distributed in tropical and subtropical areas. It is well known that this genus produces sesquiterpenes, diterpenes, acetogenic lactones, flavones and cumarines.

Experimental

Plant Material

Conyza sophiaefolia (Asteraceae, Asteroidae, Astereae), was harvested in «El Volcán», February 1998, and identified by Ing. L. A. Del Vitto, E. M. Petenatti & O. S. Giordano. A Voucher specimen is deposited at the Herbario of UNSL N° 6758.

Isolation Procedure

The dried ground aerial parts were extracted with Me₂CO, the residue obtained was dissolved with MeOH-H₂O 9:1 and partitioned with n-hexane (Extract A) and chloroform (Extract B). These residues were subjected, several times, to a combination of chromatography procedures on Si gel 60 using mixtures of n-hexane-ethyl acetate as eluents and Sephadex LH 20 with methanol as eluent.

Result and Discussion

Hawtriwaic acid [1], 2β hidroxyhardwickiic acid [2], apigenin and the diterpenes 1, 12-epi-bacchotricuneatina A and 2 [3] were isolated from extract B. Structures were determinate by EM, ¹H y ¹³C-RMN (

Table 1.

H/C	δH (Compound 1)	δC
1	1.68 br s	25.7 q
2		132.1 s
3	5.19 br t (6.0)	124.1 d
4	2.10 br t (4.0)	28.0 t
5	2.25 m	28.7 t
6		131.7 s
7	6.72 t (7.3)	145.6 d
8	2.35 m	27.0 t
9	2.30 m	38.5 t
10		134.4 s
11	5.20 br t (6.8)	125.1 d
12	2.23 m	27.4 t
13	2.45 br q (7.5)	25.1 t
14		128.2 s
15	6.28 br s	111.2 d
16	7.31 br s	142.8 d
17	7.20 br s	139.2 d
18	1.60 br s	15.8 q
19		174.3 s
20	1.60 br s	17.6 q

*200 MHz, C₆D₆.

*Mass fragments: [M⁺] m/z=316; -Me=301; -C₆H₅=247; pirilio⁺=81; C₅H₉ ⁺=69

) and confirmed by bidimentional experiments (COSY, NOESY, ROESY, HMBC, HMQC).

The anti-inflammatory activity of all the extracts has been evaluated by paw edema test [4] (

Table 2.

Product	Acute inflammation inhibit %				Dunnet’s Test
Acetonic extract	1H	3Hs.	5Hs.	7Hs.	(a) p<0.02
	-	37	45(b)	49(a)
Chloroformic extract A	14	22	45(b)	35	(b) p<0.04
n-hexane extract B	-	12	36	26	(c) p<0.002
Phenylbutazone	55	65(d)	65(c)	52(a)	(d) p<0.0003

).