Composição química do óleo essencial das folhas de Duguetia furfuracea A. St. Hill (Annonaceae) em função da variação sazonal e caracterização morfoanatômica e histoquímica

Abstract

Duguetia furfuracea A. St. Hill., Annonaceae is a subshrub found in the cerrado, popularly known as "ata-brava," "araticum-seco," "araticum," and "araticum-miúdo," used in folk medicine for the treatment of rheumatism and kidney colic. Chemical studies report the presence of major compounds in the essential oil obtained from the leaves, such as bicyclogermacrene, (E)-asarone, 2,4,5-trimethoxystyrene, α-gurjunene, and cyperenand. Seasonal factors like temperature, humidity, and hours of light may influence the production and quality of the essential oil. This study investigated the yield and variation in the chemical composition of the essential oil, morphoanatomy, histochemistry of the leaves and stem of D. furfuracea, as well as antioxidant activity, rainfall analysis, and soil chemical analysis. Monthly collections (from May 2022 to April 2023) were conducted in the municipality of Dourados MT. Essential oil extraction from the twelve samples coded as (OEDF) was performed by hydrodistillation, followed by gas chromatography-mass spectrometry (GC/MS) analysis. Morphoanatomical and histochemical characterization of leaves and stems was done using light microscopy and scanning electron microscopy. Antioxidant activity was evaluated using the DPPH reagent (2,2-diphenyl-1-picrylhydrazyl). There was variation in the essential oil yield in all months, with higher yield in July (OEDF-JL 0.062%) and lower in June (OEDF-JU 0.008%). Yield was not affected by annual precipitation rates. Soil analyses showed high iron and hydrogen content, indicating an acidic and dystroferric soil. GC/MS analysis of all samples showed β-elemene (17.5% - 5.94%), germacrene B (13.48% - 5.19%), and β-pinene (31.06% -1.08%) as major compounds. Isogeijerene C (1.02%) appeared only in OEDF-A, and δ cadinene (1.33%) in OEDF-F. Moreover, all OEDF samples exhibited antioxidant activity by free radical inhibition with IC50 values of 2.50 mg/mL (EODF-F), 2.67 mg/mL (EODF-M), 1.80 mg/mL (EODF-JL), 2.59 mg/mL (EODF-AG), 2.66 mg/mL (EODF-S), and 2.41 mg/mL (EODF-D) in DPPH. Our analysis was conducted on six samples due to similarity between months regarding the compounds found in the specimens, demonstrating antioxidant activity in all six samples. The presence of certain compounds like sabinene, γ-terpinene, β-elemene, β pinene, and germacrene B may justify this antioxidant action. Morphoanatomical analysis revealed non-glandular stellate trichomes and scales in the epidermis, phenolic compounds in both parenchymas, and oil cells found in the collenchyma and mainly in the palisade parenchyma. Histochemical studies showed the presence of essential oil in collenchyma cells and also in the palisade parenchyma. The study demonstrated that D. furfuracea has essential oil with predominant oxygenated monoterpenes and sesquiterpenes, especially β-elemene and germacrene B. Precipitation did not affect oil yield. The oil showed significant antioxidant activity attributed to components like sabinene, β-elemene, germacrene B, and γ-terpinene. Essential oil cells were found in the palisade parenchyma, with phenolic compounds in both parenchymas. It is concluded that D. furfuracea is a promising source of essential oil with seasonal variation in composition and content.