Plant Flavonoids in Mediterranean Species: A Focus on Flavonols as Protective Metabolites under Climate Stress

Flavonoids are specialized metabolites largely widespread in plants where they play numerous roles including defense and signaling under stress conditions. These compounds encompass several chemical subgroups such as flavonols which are one the most represented classes. The most studied flavonols are kaempferol, quercetin and myricetin to which research attributes antioxidative properties and a potential role in UV-defense through UV-screening mechanisms making them critical for plant adaptation to climate change. Despite the great interest in flavonol functions in the last decades, some functional aspects remain under debate. This review summarizes the importance of flavonoids in plant defense against climate stressors and as signal molecules with a focus on flavonols in Mediterranean plant species. The review emphasizes the relationship between flavonol location (at the organ, tissue and cellular scales) and their function as defense metabolites against climate-related stresses. It also provides evidence that biosynthesis of flavonols, or flavonoids as a whole, could be a crucial process allowing plants to adapt to climate change, especially in the Mediterranean area which is considered as one of the most sensitive regions to climate change over the globe.

Polyphenol contents and antioxidant activity of carob callus cultures

Carob (Ceratonia siliqua L.) is an important Mediterranean plant species with worldwide commercial and medicinal uses. The establishment of a callus culture protocol as an alternative system to produce polyphenols of chemical and pharmaceutical interest was made in the present study for the first time in carob. Explant type and the light regime are two important factors that influence morphogenic responses and biochemical production. Maximal callus induction (100 %) and biomass accumulation were obtained in cotyledon explants under both tested light regimes (16-hour photoperiod and darkness). However, leaf callus produced a higher amount of polyphenols (TPC) and flavonoids (TFC) but a lower amount of total condensed tannins (TCT) as compared to cotyledon callus. Light treatment has significantly increased TCT content but decreased the antioxidant activity in carob callus cultures. Strong and positive correlations were obtained between TPC and TFC and the antioxidant activities with correlation coefficients ranging between 0.68 and 0.98. The obtained results indicate that calli of C. siliqua have the potential for enhanced production of phenolic compounds with antioxidant activity that is favored by culture under dark condition.

Hopping or Jumping on the Cliffs: The Unusual Phylogeographical and Demographic Structure of an Extremely Narrow Endemic Mediterranean Plant

Several past and recent climatic and geological events have greatly influenced the current distribution of coastal species around the Mediterranean Basin. As a consequence, the reconstruction of the distributional history of these species is challenging. In this study, we used both chloroplast and nuclear SNPs to assess the levels of genetic differentiation, contemporary/historical levels of gene flow, and demographic history for the three only known (one mainland and two insular) populations of Eokochia saxicola, a rare Mediterranean coastal rocky halophyte. Plastid genome analysis revealed very low intraspecific haplotype variation and partial admixture among Capri and Palinuro populations with at least two independent colonization events for the Strombolicchio islet. Nuclear SNPs variation consistently identified three distinct genetic clusters corresponding to our sampling localities. Furthermore, strong genetic isolation was confirmed by both historical and contemporary levels of migration among the three populations. The DIYABC analysis identified two introductions temporally separated from Palinuro to Capri (ca.25 Mya) and subsequently to Strombolicchio (ca.09 Mya) as the most likely hypothesis for the current distribution of E. saxicola. Regardless of their small population sizes, all study sites supported high-genetic diversity maintained by outcrossing and random mating between individuals owing largely to wind pollination, an exclusive trait among Mediterranean narrow endemics. In conclusion, the patterns observed confirm that some Mediterranean endemics are not necessarily “evolutionary dead-ends” but rather represent species that have extensive demographic stability and a strong evolutionary legacy.

Effect of Fire Frequency on the Flammability of Two Mediterranean Pines: Link with Needle Terpene Content

Flammability is a major factor involved in Mediterranean plant evolution that has led to the diversity of fire-related traits according to fire regimes and fire-adaptive strategies. With on-going climate change, new fire regimes are threatening plant species if they do not adapt or acclimate. Studying flammability and terpene content variation according to the different fire frequencies in the recent fire history represents a great challenge to anticipating the flammability of ecosystems in the near future. The flammability of shoots and litter as well as the needle terpene contents of two pine species with different fire adaptive strategies (Pinus halepensis and Pinus sylvestris) were measured according to two fire modalities (0 vs. 1–2 fire events over the last 60 years). Results showed that, regardless of the species and the fuel type, flammability was higher in populations having undergone at least one past fire event even when factors influencing flammability (e.g., structural traits and hydric content) were considered. The terpene content did not vary in P. sylvestris’ needles according to the fire modality, but that of sesqui- and diterpenes was higher in P. halepensis’ needles sampled in the “Fire” modality. In addition, associations made between flammability and terpene content using random forest analyses indicated that the terpene molecules differed between fire modalities for both species and fuel types. The same results were obtained with significant terpenes driving flammability as were highlighted in the PLS analyses, especially for P. halepensis for which enhanced shoot flammability in the “Fire” modality agreed with the adaptive strategy of this species to fire.

Physicochemical, Nutritional, Microbiological, and Sensory Qualities of Chicken Burgers Reformulated with Mediterranean Plant Ingredients and Health-Promoting Compounds

The quality of chicken burgers reformulated by the partial replacement of meat by Mediterranean plant ingredients and enriched with peculiar amounts of n-3 PUFAs, Mg, Fe, Se, and folic acid, was evaluated in comparison to conventional chicken burgers. Specifically, two types of burger were developed, namely the “Sicilian burger”—based on cherry tomato and rosemary—and the “Mediterranean burger”—with basil leaves and thyme essential oil—every recipe being differentially functionalized according to the nutritional requirements of consumers, such as children, pregnant women and elderly. Mediterranean ingredients were responsible for different pH, color, and cooking loss between conventional and functional burgers. Except for n-3 PUFAs resulting poorly fortified, the functionalization with Mg, Fe, Se, and vitamin B9 was successful in all products. Considering the target consumer categories, the daily consumption of the functional burger may assure an intake of Mg, Fe, and Se equal, respectively, to 37.31–59.90%, 17.76–46.81%, and 27.20–50.05%, and a cover of vitamin B9 of 31.98–48.31% of the relative population reference intakes. Fortified products kept a good microbiological quality during 5 days of refrigerated storage, and, according to the sensorial descriptive analysis and the hedonic test, they showed a higher acceptability than conventional burgers.

Phenol Biological Metabolites as Food Intake Biomarkers, a Pending Signature for a Complete Understanding of the Beneficial Effects of the Mediterranean Diet

The Mediterranean diet (MD) has become a dietary pattern of reference due to its preventive effects against chronic diseases, especially relevant in cardiovascular diseases (CVD). Establishing an objective tool to determine the degree of adherence to the MD is a pending task and deserves consideration. The central axis that distinguishes the MD from other dietary patterns is the choice and modality of food consumption. Identification of intake biomarkers of commonly consumed foods is a key strategy for estimating the degree of adherence to the MD and understanding the protective mechanisms that lead to a positive impact on health. Throughout this review we propose potential candidates to be validated as MD adherence biomarkers, with particular focus on the metabolites derived from the phenolic compounds that are associated with the consumption of typical Mediterranean plant foods. Certain phenolic metabolites are good indicators of the intake of specific foods, but others denote the intake of a wide-range of foods. For this, it is important to emphasise the need to increase the number of dietary interventions with specific foods in order to validate the biomarkers of MD adherence. Moreover, the identification and quantification of food phenolic intake biomarkers encouraging scientific research focuses on the study of the biological mechanisms in which polyphenols are involved.

A Review and Evaluation of the Data Supporting Internal Use of Helichrysum italicum

Helichrysum italicum is a Mediterranean plant with various pharmacological activities. Despite extensive reports on the bioactivity of the plant, its clinically studied applications have not yet been reviewed. The aim of our study was to gather information on the internal use of H. italicum and its bioactive constituents to determine its efficacy and safety for human use. We reviewed research articles that have not been previously presented in this context and analyzed relevant clinical studies with H. italicum. Cochranelibrary.com revealed six eligible clinical trials with H. italicum that examined indications for pain management, cough, and mental exhaustion. Although the efficacy of H. italicum has been demonstrated both in in vitro tests and in humans, it is difficult to attribute results from clinical trials to H. italicum alone, as it has usually not been tested as the sole component. On the other hand, clinical trials provide positive information on the safety profile since no adverse effects have been reported. We conclude that H. italicum is safe to use internally, while new clinical studies with H. italicum as a single component are needed to prove its efficacy. Based on the recent trend in H. italicum research, further studies are to be expected.

Species-Specific Molecular Detection of the Root Knot Nematode Meloidogyne luci

Meloidogyne luci has been identified in various countries around the world parasitizing economically important crops and, due to its potential to cause serious damage to agriculture, was included in the European and Mediterranean Plant Protection Organization Alert List in 2017. This species shares morphological and molecular similarities with M. ethiopica and M. inornata, and a M. ethiopica group was established. Although specific primers for DNA amplification of species belonging to the M. ethiopica group have been developed previously, primers were not species-specific and molecular markers for the specific detection of M. luci are still needed. The objective of this study was to develop a SCAR marker, for detection of M. luci and discrimination from other Meloidogyne spp., based on the intraspecific variability found in RAPD markers. RAPD screening of M. luci and M. ethiopica genome was used for the identification of a specific amplification product on M. luci, which was cloned, sequenced and converted into a SCAR marker. The specificity of the designed primers (Mlf/r) was tested and produced a fragment (771 bp) for all nine M. luci isolates with no amplification for the other nine Meloidogyne spp., including M. ethiopica and M. inornata. Additionally, the proper amplification of the M. luci SCAR-marker was also successful with DNA from galls of M. luci infected tomato roots. The results obtained in this study reveal that the specific molecular detection of M. luci was achieved and the developed methodology can be used for routine diagnosis purposes, which are essential to monitor M. luci distribution and spread, in order to implement future effective and integrated nematode pest management programs.