Nicotiana tabacum Leaf Waste: Morphological Characterization and Chemical-Functional Analysis of Extracts Obtained from Powder Leaves by Using Green Solvents

Abstract

Tobacco cultivation and industrialization are characterized by the production of trillions of pre-harvest and post-harvest waste biomasses each year with the resulting negative effects on the environment. The leaves of blunt, pre-harvest waste, could be further used to obtain bioactive metabolites, i.e., polyphenols and alkaloids, for its potential cosmetic use. This study was conducted to obtain bio-compounds from pre-harvest tobacco leaf waste (var. Virginia) by applying conventional and green solvents (NaDES). Leaves and ground leaf waste were characterized based on their microscopic features. Conventional solvents, such as water, acetone, ethanol, and non-conventional solvents, such as Natural Deep Eutectic Solvents (NaDES), i.e., sucrose:lactic acid (LAS), frutose:glucose:sucrose (FGS), lactic acid:sucrose:water (SALA), choline chloride:urea (CU), and citric acid: propylene glycol (CAP) were used for bioactive extraction from tobacco waste powder. CU, FGS, and acetone/ethanol had similar behavior for the best extraction of alkaloids (6.37–11.23 mg ACE/g tobacco powder). LAS, FGS, SALA, and CU were more effective in phenolic compound extraction than conventional solvents (18.13–21.98 mg AGE/g tobacco powder). Because of this, LAS and SALA could be used to obtain phenolic-enriched extracts with lower alkaloid content rather than CU and FGS. Extracts of the powder obtained with conventional solvent or CU showed a high level of sugars (47 mg/g tobacco powder) The ABTS antioxidant capacity of tobacco leaf powder was higher in the extracts obtained with CU, FGS, and acetone (SC50 1.6–5 µg GAE/mL) while H2O2 scavenging activity was better in the extracts obtained with LAS, CAP and SALA (SC50 3.8–8.7 µg GAE/mL). Due to the biocompatibility of the NaDES with the components of tobacco leaf waste, the opportunity to apply these extracts directly in antioxidant formulations, such as cosmetics, phytotherapic, and other formulations of topic use seems promising. Furthermore, NaDES constituents, i.e., urea and organic acid can also have beneficial effects on the skin.

Morphological Characterization of Nicotiana tabacum Inflorescences and Chemical-Functional Analysis of Extracts Obtained from Its Powder by Using Green Solvents (NaDESs)

“…The stomata were slightly elevated in relation to the rest of the epidermal cells. The trichomes were similar to the types described for the leaves by Leal et al [ 29 ]. The subepidermal collenchyma was formed by 2–3 layers, followed by 10–12 layers of cortical parenchyma with intercellular air spaces; lastly, an amyliferous perivascular sheath was observed internally.…”

“…The stomata are anomocytic, slightly raised in relation to the rest of the epidermal cells ( Figure 2 C,D). The trichomes distributed on both epidermal surfaces were simple and glandular type I, IIa, IIb, IIc and IId, as previously described by Leal et al [ 29 ], for the tobacco leaves var. Virginia.…”

“…Virginia ranged from 1326 to 2711 µg GAE/mL in the extraction with DW, AW, and EW, conventional solvents; with NaDESs, the values ranged from 1305 to 3420 µg GAE/mL ( Table 3 ). The content of TPC in inflorescences was higher than in pre-harvest tobacco leaf waste [ 29 ]. SALA was more effective and selective in TPC extraction and could be considered the best solvent ( Table 3 ), followed by CU, LAS, and EW, which showed the same behavior.…”

“…This homogenous liquid is stable once the eutectic point is reached, easing its use for the extraction of bioactive compounds from plant tissues. In particular, the extraction efficiency of phenols, terpenoids, and other compounds increased when NaDESs were employed instead of traditional solvents [ 29 , 30 ]. NaDESs are stable and can extract both hydrophilic and hydrophobic compounds from plant matrix [ 25 , 26 , 27 ].…”

“…NaDESs are stable and can extract both hydrophilic and hydrophobic compounds from plant matrix [ 25 , 26 , 27 ]. These properties open a gate to the development of innovative extracts with unique phytochemical profiles and biological activities for use in pharmaceutical and/or cosmetic products [ 27 , 29 ].…”