Plants are phytochemical hubs containing antioxidants, essential for normal plant functioning and adaptation to environmental cues and delivering beneficial properties for human health. Therefore, knowledge on the antioxidant potential of different plant species and their nutraceutical and pharmaceutical properties is of utmost importance. Exploring this scientific research field provides fundamental clues on (1) plant stress responses and their adaptive evolution to harsh environmental conditions and (2) (new) natural antioxidants with a functional versatility to prevent and treat human pathologies. These natural antioxidants can be valorized via plant-derived foods and products. Cuba contains an enormously rich plant biodiversity harboring a great antioxidant potential. Besides opening new avenues for the implementation of sustainable agroecological practices in crop production, it will also contribute to new strategies to preserve plant biodiversity and simultaneously improve nature management policies in Cuba. This review provides an overview on the beneficial properties of antioxidants for plant protection and human health and is directed to the valorization of these plant antioxidants, emphasizing the need for biodiversity conservation.

Oxidative stress is an important component of many diseases including cancer, along with inflammatory and neurodegenerative processes. Natural antioxidants have emerged as promising substances to protect the human body against reactive oxygen and nitrogen species. The present study evaluates the inhibition of nitric oxide (NO) production in LPS-stimulated RAW 264.7 murine macrophages and the free radical scavenging activity of Croton linearis Jacq. leaves. UPLC-QTOF-MS analysis identified 18 compounds: nine alkaloids with a morphinane, benzylisoquinoline or aporphine nucleus, and nine O-glycosylated-flavonoids with quercetin, kaempferol and isorhamnetin as the aglycones. The crude extract (IC₅₀ 21.59 µg/mL) and the n-hexane fraction (IC₅₀ 4.88 µg/mL) significantly reduced the NO production in LPS-stimulated macrophages but with relatively high cytotoxicity (CC₅₀ 75.30 and CC₅₀ 70.12 µg/mL, respectively), while the ethyl acetate fraction also showed good activity (IC₅₀ 40.03 µg/mL) without affecting the RAW 264.7 cell viability. On the other hand, the crude extract, as well as the dichloromethane and ethyl acetate fractions, showed better DPPH and ABTS free radical scavenging activities. Considering the chemical composition and the activity observed for Croton linearis leaves, they may be considered a good source of antioxidants to combat oxidative damage-related diseases.

Croton linearis Jacq. is an aromatic shrub that has been utilized in traditional medicine in the Bahamas, Jamaica, and Cuba. Recent studies have revealed the antiprotozoal potential of its leaves. The present work is aimed to identify the volatile constituents of essential oil from the stems of C. linearis (CLS-EO) and evaluate its in vitro antileishmanial activity. In addition, an in silico study of the molecular interactions was performed using molecular docking. A gas chromatographic–mass spectrometric analysis of CLS-EO identified 1,8-cineole (27.8%), α-pinene (11.1%), cis-sabinene (8.1%), p-cymene (5.7%), α-terpineol (4.4%), epi-γ-eudesmol (4.2%), linalool (3.9%), and terpinen-4-ol (2.6%) as major constituents. The evaluation of antileishmanial activity showed that CLS-EO has good activity on both parasite forms (IC_{50Promastigote} = 21.4 ± 0.1 μg/mL; IC_50Amastigote = 18.9 ± 0.3 μg/mL), with a CC₅₀ of 49.0 ± 5.0 μg/mL on peritoneal macrophages from BALB/c mice (selectivity index = 2 and 3 using the promastigote and amastigote results). Molecular docking showed good binding of epi-γ-eudesmol with different target enzymes of Leishmania. This study is the first report of the chemical composition and anti-Leishmania evaluation of CLS-EO. These findings provide support for further studies of the antileishmanial effect of this product.

The essential oil was obtained from Croton linearis Jacq. leaves. Its chemical composition was analyzed by Gas Chromatography-Mass Spectrometry. A total of 82 compounds were identified, being the principal components: guaiol (7.93%); eudesma-4(15),7-dien-1β-ol (4.94%) and guaia-3,10(14)-dien-11-ol (4.52%). Antimicrobial activity was determined against six Candida spp., three bacteria ( Staphylococcus aureus, Escherichia coli and Pseudomona aeruginosa) and two parasites ( Leishmania amazonensis and Trypanosoma cruzi). The selectivity index (SI) was computed through the determination of it cytotoxicity on peritoneal macrophages from BALB/c mice and murine fibroblasts L929 cells. Colorimetric microdilution methods as well as direct counting in optical microscopes were performed. The essential oil showed remarkable activity against L. amazonensis (IC_{50Promastigote}: 20.0 ± 4.9 μg/mL; IC_50Amastigote: 13.8 ± 4.3 μg/mL), moderate activity against T. cruzi (IC_{50Trypomastigote}: 197.26 ± 8.7 μg/mL) and weak activity against P. aureginosa. Cytotoxicity values were CC₅₀= 89.1 ± 3.4 μg/mL for macrophages BALB/c and CC₅₀= 306 ± 110 μg/mL for L929 cells, rendering a SI of 6 for amastigote form of L. amazonensis. Croton linearis Jacq. leaf essential oil, therefore, could be a potential candidate for future investigations regarding Leishmaniasis treatment.