Crocus sativus L. has been cultivated throughout history to obtain its flowers, whose dried stigmas give rise to the spice known as saffron. Crocetin esters, picrocrocin, and safranal are the main metabolites of this spice, which possess a great bioactivity, although the mechanisms of action and its bioavailability are still to be solved. The rest of the flower is composed by style, tepals, and stamens that have other compounds, such as kaempferol and delphinidin, which have an important antioxidant capacity, and these can be applied in foods, phytopharmaceuticals, and cosmetics. The aim of this work was to provide an updated and critical review of the research on the main compounds of Crocus sativus L. flower, including the adequate analytical methods for their identification and quantification, with a focus on their bioactivity and bioavailability.

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BACKGROUND Oil mills could benefit by preparing their own aqueous extracts from olive leaves. Accordingly, the present study aimed to measure the bioactive compounds richness of such extracts, especially oleuropein. A water‐based microwave extraction procedure was developed and a selective and precise high‐performance liquid chromatography with diode array detection (HPLC‐DAD) method was validated for the determination of oleuropein and others bioactive compounds from olive leaves. RESULTS The water solubility of oleuropein was determined to be 9.5 g L−1. The extraction procedure was optimized in terms of power, olive leaf weight/water volume ratio and time of extraction, and the results revealed that 2 mg mL−1 and a microwave irradiation at 800 W for 30 s resulted in the greatest efficiency. Oleuropein was determined by the new validation method, which showed good linearity (r2 = 0.996), precision (% relative standard deviation < 10%), recovery (118.6%), and limits of detection (17.48 mg L−1) and quantification (21.54 mg L−1). Good correlation (r2 = 0.979) was obtained between oleuropein of the olive leaf extracts determined by HPLC‐DAD and by UV‐visible spectrophotometry. CONCLUSION A simple extraction method was developed and validated to obtain aqueous extract from olive leaves by microwave extraction, determining for the first time oleuropein water solubility. Validation of the method showed that oleuropein in olive leaves could be quantified when it is at least 1% of dry weight by means of HPLC‐DAD. UV‐visible spectrophotometry can be useful in oil mills because it enables the content of oleuropein and other bioactive compounds content to be determined in situ in such leaf aqueous extracts. © 2020 Society of Chemical Industry

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