INTRODUCTION:

1. Plant:

The aerial parts of the herb were collected in July 2006 from Keshavshristi, Dist – Thane of Maharashtra, India and were authenticated by Natural Products - Botany, Piramal Life Sciences Ltd., Mumbai, India and a voucher specimen (No. 041005) has been deposited in the herbarium of the Piramal Life sciences Ltd.

2. Uses in traditional medicine:

Heliotropium ovalifolium Forssk. (Boraginaceae) was used externally and internally to treat syphilitic ulcers as per ancient literature. It is also frequently used as a analgesic and anti-inflammatory. In Kenya, the leaves are chewed as a substitute for tobacco^1-3. The herb has been also reported for anti-inflammatory activity by inhibiting specific IL- 6 pro-inflammatory cytokine, along with newly isolated naphthalene derivatives (1-2) isolated ⁴.

3. Extraction and Isolation:

The aerial parts of the herb (1.2 kg) were extracted with DCM: MeOH (1:1) at room temperature to obtain 50 g of crude extract, and treated with petroleum ether in separating funnel to facilitate liquid-liquid fractionation..

The petroleum ether soluble fraction (26 g) was subjected to Si-gel CC with petroleum ether – acetone (by increasing percentage of acetone to increase polarity) - as eluent to afford 9-pooled fractions. Two active fractions were further subjected to analytical high performance liquid chromatography (HPLC) evaluation and then subjected to preparative HPLC on a 250 X 16 mm, Knauer Reverse phase C₁₈, 5 m semi preparative column using gradient mobile phase of acetonitrile and water (Time/ % ACN: 0/10, 35/100, 40/100, 42/10, 55/10) at a flow rate of 15 ml/ min and UV detection at 240 nm which provided compound 1 which was characterized as 4,7,8-Trimethoxy-naphthalene-2-carboxylic acid (80 mg) with HPLC purity: 99.49 % and compound 2 which was characterized as 6-Hydroxy-5,7-dimethoxy-naphthalene-2-carbaldehyde with HPLC purity: 99.50 % (56 mg).

4. Previously isolated classes of constituents:

Helifoline, Retronecine, Heliophenanthrone, Heliotropamide, Heliotropinone A, Heliotropinone B, Supinine ^{5 - 8}.

5. Newly isolated constituents:

Compound 1: 4,7,8-Trimethoxy-naphthalene-2-carboxylic acid (Fig. 1) (80 mg from 1.2 kg of dried material): white powder; UV max (MeOH): 270, 326, 362 nm; IR bands (KBr): 3508, 3211, 2937, 1710, 1621, 1473, 1354, 1282 and 1077cm−1; Negative MS: m/z [M-1] −261 (100%), 231, 165, 112, Positive MS: m/z [M+Na]⁺ − 285(100%), 231, 203, 165 (calcd. for C₁₄H₁₄O₅, 262).

Fig.1. 4,7,8-Trimethoxy-naphthalene-2-carboxylic acid

Table 1: ¹H NMR and ¹³C NMR data for 1 (300 MHz, CDCl₃, J in Hz and δ in ppm)

C	δ_C	δ_H	Dept –135	¹H–¹H COSY	HMBC
1	104.8	7.42 (1H,d, J 1.2)	CH		C- 2, 3, 9
2	122.3		C_Q
3	124.7	8.15 (1H,d, J 1.2)	CH		C- 1, 2, 4, 10
4	127.1		C_Q
5	125.1	7.65 (1H, d, J 9.0)	CH	H6	C- 4, 6, 10
6	118	7.32 (1H, t, J 13.8)	CH	H5	C- 5, 7, 9, 10
7	140.1		C_Q
8	154.5		C_Q
9	130.3		C_Q
10	148.8		C_Q
2- COOH	167.2		C_Q
4-OCH3	52.2	3.98 (3H, s)	CH₃		C-4
7-OCH3	62.8	3.92 (3H, s)	CH₃		C-7
8-OCH3	56.1	4.08 (3H, s)	CH₃		C-8

C_Q- Quaternary Carbon

Compound 2: 6-Hydroxy-5,7-dimethoxy-naphthalene-2-carbaldehyde (Fig. 2) (56 mg from 1.2 kg of dried material): white powder; UV max (MeOH): 270, 326, 362 nm; IR bands (KBr): 3487, 2943, 2841, 1730, 1680 and 1350 cm⁻¹; Negative LC-MS: m/z [M-1] −231 (100%), 177, 110; Positive LC-MS: m/z [M+Na]⁺ − 255 (100%), [M+1] − 233, 201, 173, 145 (calcd. for C₁₃H₁₂O₄, 232).

Fig. 2. Some HMBC correlations of 4,7,8-Trimethoxy-naphthalene-2-carboxylic acid

Fig. 3. Structure of 6-Hydroxy-5, 7-dimethoxy-naphthalene-2-carbaldehyde.

Fig. 4. Some HMBC correlations of 6-Hydroxy-5, 7-dimethoxy-naphthalene-2- carbaldehyde

Table 2: ¹H NMR and ¹³C NMR data for 2 (500 and 300 MHz, CDCl₃, J in Hz and δ in ppm)

C	δ_C	δ_H	Dept –135	¹H–¹H COSY	HMBC
1	129.9	7.86 (1H,s, J 1.2)	CH		C- 3, 8, 9, 10, CHO
2	149.9		C_Q
3	127.4	7.71 (1H,d, J 8.5)	CH		C- 1, 2, 5, 9
4	118.2	7.36 (1H, d, J 9.0)	CH		C- 2, 5, 9, 10
5	140.5		C_Q
6	132.6		C_Q
7	155.4		C_Q
8	100.6	7.30 (1H, t, J 11.0)	C_H		C- 1, 7, 9, 10, CHO
9	130.2		C_Q
10	123.4		C_Q
2- CHO	191.7	10.02 (1H, s)	CH
5-OCH3	62.6	3.93 (3H, s)	CH₃		C-5, 7-OCH3
7-OCH3	56.1	4.1 (3H, s)	CH₃		C-7, 5-OCH3
6-OH	132.6	6.50 (1H, s)

C_Q- Quaternary Carbon

ACKNOWLEDGEMENTS:

Special thanks to Natural products – Botany Deptt. for the collection and identification of the plant and the Analytical Sciences, Piramal Life Sciences, for recording IR, LC-MS and NMR spectra.

REFERENCES:

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Received on 09.10.2009 Modified on 29.10.2009

Asian J. Research Chem. 2(4):Oct.-Dec. 2009 page 571-573