Isolation of Major Active Antibacterial Compounds of Sumac Fruit (Rhus coriaria L.)

Background: Infectious diseases are still one of the main causes of death according to the World Health Organization (WHO) reports. Plants due to their biochemical metabolites have been considered as one of the important sources for investigation in this field. Ethnobotanical and ethnopharmacological researches are considered effective in developing new anti-infectives. Sumac (Rhus coriaria L.) has been used as an anti-infective agent by ancient Iranian medical sages. Objectives: The aim of this study was to isolate bioactive agents of sumac epicarp with probable antibacterial activity. Materials and Methods: Grounded epicarp of sumac fruit was fractionated with different solvents. The fractions were dried and subjected to antibacterial investigation. Ethyl acetate fraction showed the strongest antibacterial activity. This fraction was further investigated through TLC-bioautography which led to the isolation of two crystallized compounds. The structure of these compounds (1 and 2) was identified using spectroscopic techniques. Isolated compounds were tested for antimicrobial activities. Results: Compound 1 which was named 1,2-dioxo-6-hydroxycyclohexadiene-4-carboxilic acid was isolated from R. coriaria L. for the first time. It showed antibacterial activity against Staphylococcus aureus (minimum inhibitory concentration [MIC] = 0.02%). Compound 2 which was identified as gallic acid showed weak antibacterial effects on both gram-positive and gram-negative bacteria (MIC > 0.1%). Conclusion: This is the first report about the chemical structures of antibacterial constituents of R. coriaria L. Previous studies have shown anti-methicillin-resistant S. aureus (MRSA) activity of sumac total extract. Compound 1 as the most effective anti-S. aureus component of sumac extract would be responsible for this activity and could be the subject matter for future investigations.