Saffron petal waste as a source of natural antimicrobials: comparative analysis of extraction methods

Saffron (Crocus sativus L.) petals are a main by-product that is produced in large quantities, but it is mainly discarded as saffron processing waste. However, the petals are worth considering because they are cheaper than the stigma and are used in traditional medicine as an antispasmodic, anti-anxiety, anti-tumor, and anti-depressant. The present study was designed for the first time in Iran to investigate the effect of different extract extraction methods and types of solvent on the antimicrobial activity of C. sativus petal extract. The petals of C. sativus were collected from the Talkhonche region, Isfahan, Iran in November 2022. The extraction was done using classic methods (Soxhlet, percolation, boiling, digestion, brewing, simple and shaking maceration) and modern methods (ultrasonic waves and supercritical fluid) with ethanol and water solvents. The antimicrobial activity of the extracts against some of the clinical microbial strains was investigated by the Agar well-diffusion method and determination of the minimum inhibitory concentration and minimum bactericidal concentration (MIC and MBC). Based on the ANOVA results extraction method and type of solvent had a significant effect on yield and antimicrobial activity of C. sativus petal extract (P ≤ 0.01). The highest and lowest yields were related to the extract obtained by the Soxhlet method with ethanol solvent (~ 49.2%) and the supercritical method with water solvent (~ 2%). The highest inhibition halo of C. sativus petal extracted by ultrasound method with ethanol (~ 23 mm) and shaking maceration method with ethanol (~ 22 mm) was against Gam-positive Staphylococcus epidermidis, which was almost similar to rifampin. Therefore, it seems that the ethanolic extract of C. sativus petals obtained by some modern or classical methods can be used as a possible option and potential to produce inexpensive natural antimicrobial drugs against some bacterial strains. Therefore, the cheap waste of C. sativus fields can be turned into an economic product.