Sustainable Processing of Floral Bio-Residues of Saffron (Crocus sativus L.) for Valuable Biorefinery Products

Abstract

Tepals constitute the most abundant bio-residues of saffron (Crocus sativus L.). As they are a natural source of polyphenols with antioxidant properties, they could be processed to generate valuable biorefinery products for applications in the pharmaceutical, cosmetic, and food industries, becoming a new source of income while reducing bio-waste. Proper storage of by-products is important in biorefining and dehydration is widely used in the herb sector, especially for highly perishable harvested flowers. This study aimed to deepen the phytochemical composition of dried saffron tepals and to investigate whether this was influenced by the extraction technique. In particular, the conventional maceration was compared with the Ultrasound Assisted Extraction (UAE), using different solvents (water and three methanol concentrations, i.e., 20%, 50%, and 80%). Compared to the spice, the dried saffron tepals showed a lower content of total phenolics (average value 1127.94 ± 32.34 mg GAE 100 g−1 DW) and anthocyanins (up to 413.30 ± 137.16 mg G3G 100 g−1 DW), but a higher antioxidant activity, which was measured through the FRAP, ABTS, and DPPH assays. The HPLC-DAD analysis detected some phenolic compounds (i.e., ferulic acid, isoquercitrin, and quercitrin) not previously found in fresh saffron tepals. Vitamin C, already discovered in the spice, was interestingly detected also in dried tepals. Regarding the extraction technique, in most cases, UAE with safer solvents (i.e., water or low percentage of methanol) showed results of phenolic compounds and vitamin C similar to maceration, allowing an improvement in extractions by halving the time. Thus, this study demonstrated that saffron tepals can be dried maintaining their quality and that green extractions can be adopted to obtain high yields of valuable antioxidant phytochemicals, meeting the requirement for a sustainable biorefining.

Six Common Herbs with Distinctive Bioactive, Antioxidant Components. A Review of Their Separation Techniques

“…Water, ethanol–water, and CO 2 –ethanol mixtures appeared until recently as the only solvents used for the recovery of compounds. In a research paper of 2021 [ 207 ], methanol was used for the first time, in mixtures with water, as potential solvent for petals extraction. The extraction methods from the literature together with their respective optimization parameters are summarized in Table 8 .…”

“…They performed CSE (agitation) of petals with hot water (66 °C) at a solid/liquid ratio of 1/36, for 104 min and yielded TPC 7.21 mg/g, TFC 1.01 mg/g, and TAC 1.89 mg/g. Additionally, Stelluti et al [ 207 ] macerated petals powder with water under stirring (1000 rpm) in the dark for 30 min, at 21 °C, yielding TPC 11.4 mg/g and TAC 3.45 mg/g.…”

“…As far as the assisting techniques are concerned, we can notice that solid/liquid ratios ranged between 1/50 and 1/20, and durations 2–45 min [ 207 , 211 , 213 ]. Compared with the respective conventional extractions the TPC yields varied between 96 and 129% of the theoretical values.…”

Saffron (Crocus sativus L.) Flower Water Extract Disrupts the Cecal Microbiome, Brush Border Membrane Functionality, and Morphology In Vivo (Gallus gallus)

“…Most of these therapeutic effects are accredited to three major bioactive compounds: crocin (responsible for saffron’s color), picrocrocin (its bitter taste), and safranal (its aroma) [ 10 ]. These compounds can be found in the tepals as well [ 1 , 4 , 11 , 12 , 13 ]. Additionally, the floral bio-residues have numerous flavonoids including kaempferol (84% of total flavonols), quercetin, delphinidin, petunidin, and malvidin [ 4 ].…”

Special Issue Editorial: Isolation and Analysis of Characteristic Compounds from Herbal and Plant Extracts

“…By isolating and characterizing the compounds in extracts, it helps to elucidate the pharmacological activities from the extract and explains the biochemical metabolism of compounds inside plants and herbs. In this Special Issue, thirteen research articles [1][2][3][4][5][6][7][8][9][10][11][12][13] and two reviews [14,15] focusing on isolation and analysis of compounds from plant extracts have been published. This Special Issue of Plants covers a broad range of recent findings of isolation, profiling, analysis of compounds from herbal and plant extracts, quality control, and standardization of processing extracts with characterized compounds.…”