The antibacterial activity of the aqueous, ethanol, methanol and petroleum ether Soxhlet extracts of sundried stem bark of Spathodea campanulata P. Beauv. (Bignoniaceae) was investigated by testing the extracts against B. subtilis, E. coli, P. aeruginosa and S. aureus. The minimum inhibitory concentration (MIC) of the methanol extract was determined against the four bacteria strains and C. albicans using the broth dilution method. Four topical products were prepared by incorporating the methanol extract of S. campanulata (20 % w/w) into aqueous cream, soft paraffin, emulsifying ointment and simple ointment bases and evaluated for their in vitro antimicrobial efficacy. The effect of storage time on the activity of the methanol extract of S. campanulata and S. campanulata extract incorporated in aqueous cream base was also investigated. The methanol and ethanol extracts showed good activity while the aqueous and petroleum ether extracts exhibited little activity. The methanol extract showed the best antibacterial activity. The MIC of the methanol extract of S. campanulata was: C. albicans (45 -50 mg/ml), B. subtilis and E. coli (50 -55 mg/ml), P. aeruginosa (60 -65 mg/ml), S. aureus (145 -150 mg/ml). Antimicrobial activity of S. campanulata in the topical bases was in the order: aqueous cream > emulsifying ointment > simple ointment > white soft paraffin. Antimicrobial activity of S. campanulata in aqueous cream decreased (p < 0.05) upon storage at room temperature for 6-months. The antifungal activity of the methanol extract of S. campanulata was reduced (p < 0.05) upon storage while antibacterial activity was largely unaffected.

Bacterial conjugation is the main mechanism for the transfer of multiple antibiotic resistance genes among pathogenic microorganisms. This process could be controlled by compounds that inhibit bacterial conjugation. In this study, the effect of allyl isothiocyanate, Lsulforaphane, benzyl isothiocyanate, phenylethyl isothiocyanate and 4-methoxyphenyl isothiocyanate on the conjugation of broad host range plasmids, which harbor various resistance genes in Escherichia coli were investigated; pKM101 (IncN), TP114 (IncI 2) , pUB307 (IncP) and the low copy number IncW plasmid R7K. Benzyl isothiocyanate (32 mg/L) significantly reduced the conjugal transfer of pKM101, TP114 and pUB307 to 0.3±0.6%, 10.7±3.3% and 6.5±1.0%, respectively. L-sulforaphane (16 mg/L, transfer frequency 21.5±5.1%) and 4-methoxyphenyl isothiocyanate (100 mg/L, transfer frequency 5.2±2.8%) were the only compounds that showed anti-conjugal specificity by actively reducing the transfer of R7K and pUB307, respectively.

This study evaluated the wound healing potential of Spathodea campanulata stem bark in Sprague Dawley rats using the excision wound model. The methanol extract contained glycosides, flavonoids and tannins, and was relatively stable when stored at the room temperature for six (6) months. Solvent-free, semi-solid extract of S. campanulata was incorporated into an aqueous cream and applied (10 % w/w and 20 % w/w) on excision wounds of thirty two (32) rats. Cicatrin(®) cream was used as a standard wound healing agent. Prior to the remedial cream application, done later on twice daily, sixteen (16) rats had their wounds infected with Staphylococcus aureus, while in the remaining sixteen the wounds were kept clean. The surface area of the excision wounds was monitored planimetrically every four (4) days until a complete wound closure or healing took place. Excision wounds treated with 20 % w/w Spathodea cream and Cicatrin(®) cream showed a rapid and comparable decrease (p > 0.05) in wound size. In uninfected wounds, both 20 % w/w Spathodea cream and Cicatrin(®) cream application resulted in ∼ 95 %-wound closure seen on Day 20, and a complete closure seen on Day 24. In infected wounds, both 20 % w/w Spathodea cream and Cicatrin(®) cream administration led to ∼ 91 %-wound closure on Day 24 and a complete wound contraction on Day 28. The results of this study justify the folkloric use of S. campanulata stem bark to the effect of wound treatment.

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