Humic substances from green compost increase bioactivity and antibacterial properties of essential oils in Basil leaves

Abstract

Background The Essential oils (EOs) are important bioactive secondary metabolites of aromatic plants, such as Basil, and find extensive utilization in pharmaceutical sector as therapeutic agents. A more eco-friendly industrial production of EOs requires new sustainable methods to improve yield and quality of these bioactive compounds in aromatic plants. Here, we evaluated the biostimulation effects of natural organic materials, such as humic substances (HS) extracted from a humified green compost made with artichoke biomasses. Results The molecular characteristics of HS from green compost were determined by 13C-CPMAS NMR spectroscopy and offline pyrolysis–gas chromatography/mass spectrometry and combined to the bioactivity of the EOs extracts to investigate the structural–activity relationship. Basil plants were grown under HS treatments at different concentrations and the yield, the chemical composition and the antioxidant and antimicrobial properties were determined for EOs extracted by steam distillation method from Basil leaves. HS showed a positive effect on total extraction yield of the most bioactive EO components, with a progressive enhancement of abundance for eugenol, eucalyptol and geranyl acetate with increasing HS concentrations. Humic biostimulation influenced the EOs antioxidant proprieties, as well as their antimicrobial activity against some common Gram-negative bacterial strains such as Klebsiella pneumoniae. The HS biostimulation of Basil plants was associated to their structural hydrophobic characteristics that may have favoured the interactions with the Basil rhizome and to specific bioactive molecular components, such as a lignin-derived phenols and polar saccharidic and aminoacidic compounds. Conclusions Our results support the potential use of humic substances from green compost as promising effective biostimulants to improve the production and bioactive properties of EOs in aromatic plants. Graphic Abstract

Antiflammatory activity and potential dermatological applications of characterized humic acids from a lignite and a green compost

“…The most abundant lignin monomers were the oxidized products of both di- and tri-methoxy phenylpropane molecules, with aldehydic-, ketonic-, benzoic-acid, and benzene-propenoic acids as main components (Figure S1 ; Table S2 ). This finding combined with the lower yields of less altered lignin units indicated the prevalent incorporation in HA-CYN of bio-available lignin fragments from composted plant residues 18 , 19 , 25 . In the wide range of long chain alkanoic acids (Table S1 ), the largest abundance was that of the ubiquitous hexadecanoic and octadecanoic homologues, while a prevalence of even-carbon linear chains suggests a plant origin 25 .…”

“…The distinct signals around the broad resonance at 30 ppm in the 0–45 ppm range, are due to of methyl and methylene groups in alkyl chains of various linear lipid compounds, while the less intense peaks at 40–45 ppm may be due to tertiary (CH) and quaternary (C–R) carbons in assembled rings of sterol, flavonoids and lignans 25 . The prominent resonance at 57 ppm is mainly assigned to methoxy substituents in aromatic lignin monomers, with an additional contribution of C–N bonds of peptidic moieties 18 , 19 . The signals in the 60–110 ppm chemical shift pertain to various C–O groups in carbohydrates and polysaccharides from plant tissues.…”

“…In this context, natural organic derivates, such as humic acids (HA), found several applications in different pharmaceutical fields like medicine and veterinary science due to the acknowledged antiviral, antimicrobial, profibrinolytic, antiflammatory and estrogenic activities 17 , 18 . Moreover, these bioactive molecules can be easily isolated from recycled biomasses such as green compost from agricultural wastes, thus widening the value of recycled biomasses within the circular economy framework 18 , 19 . Some humic materials like fulvic acids have been used in the topical treatment of dermatitis and psoriasis, rheumatoid arthritis and eczema 20 , 21 .…”

Humic Substances in Combination With Plant Growth-Promoting Bacteria as an Alternative for Sustainable Agriculture

“…The application of HSs in basil was able to influence the antioxidant properties of essential oil, as well as its antibiotic activity against bacteria such as Klebsiella pneumoniae. This effect can be attributed to the ability of HSs to affect secondary plant metabolism, promoting a higher yield of phenolic compounds and, consequently, a greater antimicrobial activity of essential oils, which is afeature of great interest for biological control (Verrillo et al, 2021). The application of HA also suppressed the injury caused by grape nematodes, decreasing nematode fertility and fecundity (Kesba and El-Beltagi, 2012).…”

Effects of Biostimulants on the Chemical Composition of Essential Oil and Hydrosol of Lavandin (Lavandula x intermedia Emeric ex Loisel.) Cultivated in Tuscan-Emilian Apennines

“…For this reason, there are numerous efforts to increase the yield of EOs starting from the application of agricultural interventions, as well as improvements in the extraction technique. In particular, agricultural research is involved in increasing the yield of EO and improving the quality composition [9,10]. In this context, progress has been made in understanding the underlying factors of EO production by plants.…”