*2.2. Basil*

Basil (*Ocimum basilicum* L.) belongs to the Lamiaceae family and it is one of the most important aromatic herbs cultivated worldwide as it flourishes under a wide range of climatic conditions. Basil cultivated both in open-field and under greenhouse conditions is an essential ingredient of renowned pesto sauce (widely consumed in Italy), while it is also used for fresh consumption and as a culinary spice [57]. In addition, the extraction of essential oils from basil is of high interest to both cosmetic and pharmaceutical industries. Basil comes in a wide variety of types, conventionally classified into seven morphotypes: (i) Large-leafed "Italian" basil, (ii) tall, slender basil, (iii) dwarf "Bush" basil, (iv) compact "Thai" basil, (v) purple basil (with clove-like aroma), (vi) citriodorum basil (flavored types), and (vii) purpurascens basil (sweet purple-colored basil) [58]. The herbs of the Lamiaceae family, such as basil, are characterized by strong antioxidant capacity. Basil in particular is a rich source of phenolic compounds, including phenolic acids such as rosmarinic, caffeic, chicoric and caftaric acids [59–61], vitamin C, and carotenoids such as lutein and β-carotene [62]. Furthermore, certain purple/red cultivars also have important concentrations of the hydrophilic anthocyanins, especially the "Dark Opal", "Purple Ruffles", and "Rubin" cultivars" [61,63].

The main carotenoids detected in basil are mostly lutein and β-carotene; but Calucci et al. [64] ranks basil first among aromatic herbs with respect to the concentrations of xanthophyll carotenoids. In the study of Kopsell et al. [62], the main detected carotenoids in sweet basil were identified as lutein, β-carotene, and zeaxanthin, and significant differences in carotenoid profiles were observed between different growing conditions (open-field versus greenhouse) and cultivars ("Cinnamon", "Genovese", "Italian large leaf", "Nufar", "Osmin purple", "Red Rubin", "Spicy bush", and "Sweet Tai"). According to Marchand et al. [38] and Johnson et al. [40], the frequent consumption of vegetables and herbs was more strongly correlated with reduced risk of certain types of cancer and degenerative ophthalmic diseases, in comparison to the ingestion of monomolecular carotenoid supplements. In addition

to carotenoids, basil is considered also an important source of vitamin C. It is well established that vitamin C is crucial for immune and antioxidant functions, and according to the WHO, 80–90 mg of vitamin C should be ingested daily [65]. However, due to the water solubility of ascorbic acid, regular dietary intake is essential to normal metabolic functioning [66]. According to Murarikova and Neugebauerova [65] the ascorbic acid content varied from 34.3 to 220.0 mg/kg fresh weight among the tested varieties ("Dark Green", "Lettuce Leaf", "Mammolo Genovese", "Manes", "Ohre", "Purple Opal", and "Red Rubin") and the different growing seasons.

Rosmarinic acid is noted in the scientific literature as the most abundant phenolic constituent of basil [59,60]. On the other hand, a study carried out by Kwee and Niemeyer [61] showed that 9 over 15 basil cultivars contained other caffeic acid derivatives, such as chicoric acid, in higher concentrations than rosmarinic acid. Moreover, the antioxidant and antimicrobial properties of "Napoletano" green and purple basil were analyzed by Tenore et al. [67], who reported that the main phenolic acids in purple basil were rosmarinic, ferulic and gallic acid; while in green basil, the most abundant phenolic constituents were gallic acid, followed by rosmarinic and ferulic acids. Interestingly, the functional molecule rosmarinic acid detected in "Napoletano" type basil was by far higher than what on average has been reported for other common varieties such as "Sweet basil", "Thai basil", "Genovese Italiano", and "Purple Petra" (112, 128, 117, and 352 per 100 g fresh weight, respectively) [59]. The main anthocyanins detected in purple basil extract were cyanidin-based *p*-coumaril and malonil acids, acting as powerful antioxidants with potential use as medicinal agents [68]. Tenore and co-workers also demonstrated in the same study that extracts of "Napoletano" green and purple basil both had a broad antimicrobial spectrum able to reduce the growth of all human pathogenic and food spoilage bacteria and molds tested [67].

Regarding the health-promoting effects of basil, several preclinical and clinical studies showed that extracts from basil, particularly the purple one, may alleviate hyperglycemia associated with type 2 diabetes [69,70]. The anti-diabetic beneficial effects of basil extract may be due in part to catechin and especially to rosmarinic acid, which has been found to inhibit key enzymes such as α-amylase, α-glucosidase, and aldose reductase [71–73]. In addition to being anti-diabetic, basil extract may also be an efficient tool against hyperlipidemia by effecting lower cholesterol and triglyceride levels in the blood [74,75]. Reduced uptake of lipids and lower values of total cholesterol and low density lipoprotein may reduce the risk of cardiovascular diseases.
