Introduction

Sida rhombifolia Linn. (Syn. S. rhomboidea Linn., Family-Malvaceae, Bengali Name-Lal Berela) is a small erect undershrub, which grows all over Bangladesh ₁ . The stems are used to treat rheumatism and tuberculosis ₂ . It is also reputed as anthelmintic and sedative. The roots are used in epilepsy, neurological problem, and fever and heart diseases ₃ . Fruits are as known to be antibacterial and antifungal. The whole plant in combination with other drugs is prescribed as an anitdote to snake and scorpion venom ₄ . Previous phytochemical investigations of Sida species resulted in the isolation of stigmasterol, stigmatenol and β-sitosterol. We, herein, report the preliminary antimicrobial, cytotoxic and antioxidant activities of the organic extractives as well as isolation of daucosterol from the n-hexane soluble fraction of S. rhomboidea for the first time.

Materials and Methods

General experimental procedure

Plant Material

Extraction and isolation

Bioassays

Results and Discussion

Compound 1 was isolated from the n-hexane soluble fraction of methanolic extract of the stems of S. rhomboidea by repeated chromatographic separation and purification over silica gel. The structure of the isolated compound was determined by comparison of ¹ H NMR data with previously reported values ₉ as well as co- TLC with authentic sample. Although it has previously been reported from many plants, this is the first report of its isolation from S. rhomboidea.

Figure 1

In the antimicrobial screening, the extractives as S. rhomboidea exhibited mild to moderate antimicrobial activity. The zone of inhibition produced by the carbon tetrachloride and dichloromethane soluble fractions of methanolic extract ranged from 8-13 and 8-12 mm respectively (Table -1). The n-hexane and aqueous soluble fractions did not show inhibit the growth of microorganisms.

Figure 2

Table 1. Antimicrobial activity of extractives at 400 µg/disc.

CT: carbon tetrachloride soluble fraction of the methanolic extract; DCM: dichloromethane soluble fraction of the methanolic extract; KAN: standard kanamycin disc (30µg/disc).

Following the procedure of Meyer ₇ , the lethality n-hexane (HX), carbon tetrachloride (CT), dichloromethane (DCM) and aqueous (AQ) soluble fractions of the methanolic extract to brine shrimp was determined on. Table 2 shows the results of the brine shrimp lethality testing after 24 hours of exposure to the samples and the positive control, vincristine sulphate. The LC₅₀ obtained from the best fit line slope were found to be 0.84, 5.89, 7.6 and 2.7 µg/ml for n-hexane, carbon tetrachloride, dichloromethane and aqueous soluble materials, respectively (Table -2). In comparison with the positive control (vincristine sulphate, LC₅₀ 0.46µg/ml) the cytotoxicity exhibited by the n-hexane, methanolic aqueous, carbon tetrachloride fraction of methanolic extract was significant.

Figure 3

Table 2. LC data of test samples of

¬¬¬¬VS: vincristine sulphate (std); HX: n-hexane soluble fraction of methanolic extract; CT: carbon tetrachloride soluble fraction of methanolic extract; DCM: dichloromethane soluble fraction of methanolic extract; AQ: aqueous soluble fraction of methanolic extract.

The antioxidant activity of various fractions of the methanolic extract was also determined. Table-3 shows antioxidant activity of the test samples. Here, tert butyl-1-hydroxy toluene (BHT) was used as positive control. The IC₅₀ values for n-hexane, carbon tetrachloride, dichloromethane and methanolic aqueous were found to be 316, 217, 20 and 32 µg/ml, respectively. In comparison with positive control (BHT) the antioxidant activity exhibited by the dichloromethane and aqueous soluble fractions of methanolic extract was significant. The pure compound 1 was also tested for antioxidant activity, but no significant inhibitory capacity was found (data not shown in table-3).

Figure 4

Table 3. IC data of test samples of

BHT: tert butyl-1-hydroxy toluene (Std); HX: n-hexane soluble fraction of methanolic extract; CT: carbon tetrachloride soluble fraction of methanolic extract; DCM: dichloromethane soluble fraction of methanolic extract; AQ: aqueous soluble fraction of methanolic extract.

The results of antimicrobial, cytotoxic and antioxidant activities support the folk uses of S. rhomboidea in various diseases.

Acknowledgement