Mentha longifolia L. and Citrus reticulata L. Essential Oils as Wood-Biofungicides -

Mentha longifolia L. and Citrus reticulata L. Essential Oils as Wood-Biofungicides

Essential oils (EOs) from aerial parts from Mentha longifolia L. and Citrus reticulata L., were tested for their antifungal activity by the vapor method against four common fungi, Aspergillus flavus, A. niger, A. fumigatus, and Fusarium culmorum through GCMS and confirmed by SEM examination as the oils applied on wood samples. The most abundant compounds identified in the EO from M. longifolia were menthone and eucalyptol; in C. reticulata EO, they were β-caryophyllene, β-caryophyllene oxide, and β-elemene. EOs from M. longifolia and C. reticulata, at 500 and 250 µL/mL, showed potent antifungal activity against A. flavus and A. fumigatus, with 100% fungal mycelial inhibition growth (FMIG). F. culmorum completely inhibited (100% FMIG) EOs from M. longifolia and C. reticulate applied at 500 µL/mL. Both oils possessed good wood-biofungicide activity with the vapor method, as clearly shown by the SEM examination. These activities suggest their possible use as natural wood preservatives

Extraction of Essential Oils

Aerial parts of Mentha longifolia L. and leaves of Citrus reticulata L. were used for the extraction. About 150 g of air-dried plant material from M. longifolia and another 150 g of fresh leaves from C. reticulata were extracted by the hydrodistillation method using a Clevenger apparatus. The plant materials were inserted in a 2 L flask with 1.5 L of distilled water and heated for 3 h under refluxing. M. longifolia and C. reticulata yielded EOs of 2.5% and 1.12%, respectively, of the dried material.

Results

Essential Oil Composition

The chemical composition of the EO from M. longifolia aerial parts, from which 8 compounds were identified. The main constituents were menthone (48.00%), eucalyptol (21.66%), and pulegone (12.09%). The chemical compounds of the EO from C. reticulata aerial parts, which were composed of 48 compounds, where the main compounds were β-caryophyllene (15.57%), β-caryophyllene oxide (7.04%), β-elemene (6.39%), ᵞ-elemene (5.62%), β-bisabolene (4.86%), spathulenol (4.74%), β-caryophyllene (4.53%), longifolene (4.40%), ᵞ-gurjunene (3.74%), geranyl acetate (3.34%), α-bergamotene (3.19%), linalyl acetate (2.96%), germacrene D (2.28%), nerol (2.24%), D-limonene (2.14%), and geraniol (2.00%).

Antifungal Activity of the Essential Oils

M. longifolia and C. reticulate EOs, at the concentrations of 500 and 250 µL/mL, antifungal activity was observed against A. flavus and A. fumigatus, with 100% fungal mycelial inhibition growth (FMIG), which was higher than the FMIG values from Sertaconazol (91% and 88.66%, respectively). C. reticulate and M. longifolia EOs, at 125 µL/mL, showed activity against the growth of A. fumigatus, with FMIG values of 98% and 95%, respectively. M. longifolia EO, at 500 and 250 µL/mL, showed 100% FMIG against A. niger, while C. reticulata EO showed FMIG values of 100% and 97%, at 500 and 250 _L/mL, respectively, which were higher than the value from Sertaconazol (87%). The EOs from M. longifolia and C. reticulata completely inhibited the growth of F. culmorum, with 100% FMIG at the concentration of 500 µL/mL, which is higher than the value from Sertaconazol (88.33%). Additionally, at the concentration of 250 µL/mL, the EO from C. reticulata showed activity against F. culmorum (FMIG value of 85.66%). Furthermore, EOs at lower concentrations (65 and 125 µL/mL) showed FMIG percentages against the studied molds. Therefore, those two concentrations were used for the application on wood by the vapor method.

Application of Oils on Wood Samples

Oils from M. longifolia and C. reticulata, at 125 µL/mL, showed inhibition zone (IZ) values around the treated Pinus roxburghii wood samples compared to the control treatment (wood without oils), where the growth of fungi was observed. M. longifolia, applied to wood at 125 µL/mL, showed an IZ value of 7.33 mm against the growth of A. flavus. An IZ value of 15.33 mm was shown for wood treated with C. reticulata oil at 125 µL/mL against A. fumigatus. M. longifolia, at 65 and 125 µL/mL, showed potent antifungal activity against A. niger when applied to wood samples with IZ values of 8 and 21.33 mm, respectively. Wood treated with C. reticulata and M. longifolia, at 125 µL/mL, showed IZ values of 3.66 and 2.33 mm, respectively, against the growth of F. culmorum.

Conclusions

The present research confirmed the potent antifungal activities of essential oils from Mentha longifolia and Citrus reticulata. Essential oils from M. longifolia and C. reticulata are of great interest with regard to their antifungal activities against Aspergillus flavus, A. niger, A. fumigatus, and Fusarium culmorum when applied as biopreservation for wood. Essential oil from M. longifolia, at 125 µL/mL, applied to Pinus roxburghii wood, showed an inhibition zone (7.33 mm) around the wood samples when inoculated with A. flavus; the inhibition zone was 15.33 mm when the wood samples were treated with the essential oil from C. reticulata against A. fumigatus and 21.33 mm when treated with the oil from M. longifolia against A. niger. Additionally, both oils showed the lowest inhibition zones against F. culmorum when applied to wood samples. By SEM examination, wood anatomical features have been clearly shown to have no fungal growths when the wood samples were treated with both oils at 125 µL/mL. These activities suggest their possible use as natural preservative additives and in the food industry

Reference:

Ali, H.M., Elgat, W.A.A., El-Hefny, M., Salem, M.Z., Taha, A.S., Al Farraj, D.A., Elshikh, M.S., Hatamleh, A.A. and Abdel-Salam, E.M., 2021. New approach for using of Mentha longifolia L. and Citrus reticulata L. essential oils as wood-biofungicides: GC-MS, SEM, and MNDO quantum chemical studies. Materials, 14(6), p.1361.