Plectranthus amboinicus (Lour) Spreng and Plectranthus amboinicus “Variegata” Ehrh are medicinal plants used in the treatment of diseases, such as inflammation and cancer. These plants are related species that differ morphologically due to the variegation in the leaves. Variegation in plants has been widely observed and may interfere in the production of secondary metabolites and other plant bioactives. This study was aimed in compare the total flavonoid content and the antioxidant activity of P. amboinicus and P. amboinicus “Variegata” crude extracts. P. amboinicus and P. amboinicus “Variegata” were grown under organic cultivation at Jucuruaba Experimental Farm of the Instituto Capixaba de Pesquisa, Assistência Técnica e Extensão Rural (Incaper). The aerial part of the plants was collected, dried at room temperature (36-38 ºC) and ground by a mechanical grinder. The dried plant material was macerated in EtOH/H2O (70:30 v/v) for 5 days and filtered. The resulting liquid from the filtration was stored away from light and the solid phase was reserved and subjected to the same maceration conditions for a further 2 times. The solvent was evaporated under reduced pressure at 65-70 °C to obtain the crude extracts of each plant. Total flavonoid content was measured using the colorimetric method described for Zhishen et al. (1999), with minor modifications. The results were expressed as equivalent of microgram (µg) of rutin per milligram (mg) of dried mass of extract. Antioxidant activity was measured using DPPH (2,2-diphenyl-1-picryl-hydrazyl) method described by Re et al. (1999) and ABTS (2,2′-azinobis-(-3-ethylbenzothiazoline-6-sulfononic acid)) assay described by Harzallah et al. (2016). Extracts antioxidant activity was evaluated using extract diluted in the concentration of 1000.00, 500.00, 250.00, 125.00, 62.50, 31.25 and 15.63 µg.mL-1 and results were expressed as percentage inhibition of the free radical. P. amboinicus extract showed total flavonoid content of 10.05 ± 0.44 µg.mg-1. Following the DPPH test, P. amboinicus extract reached 3.53-74.52% of DPPH inhibition and in ABTS assay reached 0.00-55.50% of ABTS inhibition. P. amboinicus “Variegata” extract presented total flavonoid content of 46.48 ± 3.06 µg.mg-1. In the DPPH test, P. amboinicus extract reached 2.08-92.10% of DPPH inhibition and following the ABTS assay reached 1.99-63.73% of ABTS inhibition. These results suggest that P. amboinicus “Variegata” showed higher total content of flavonoids, as well as showed stronger antioxidant activity in a comparison to P. amboinicus. Its suggests that the variegation observed in P. amboinicus may interfere in secondary metabolites production, such as flavonoids, and is probably related to the increase in antioxidant activity.

References: 1 - Zhishen, J., Mengcheng, T., Jianming, W. The determination of flavonoid contents in mulberry and their scavenging effects on superoxide radicals. Food Chemistry, v. 64, n. 4, p. 555–559, 1999; 2 - Harzallah, A., Bhouri, A.M., Amri, Z., Soltana, H., Hammami, M. Phytochemical content and antioxidant activity of different fruit parts juices of three figs (Ficus carica L.) varieties grown in Tunisia. Ind. Crop. Prod., v. 83, 225-267, 2016. 3 - Re, R., Pellegrini, N., Proteggente, A., Pannala, A., Yang, M., Rice-Evans, C. Antioxidant activity applying an improved ABTS radical cation decolorization assay. Free Radical Bio. Med., v. 26, 1231-1237, 1999.

Acknowledgments: Fundação de Amparo à Pesquisa e Inovação do Espírito Santo (FAPES); Instituto Capixaba de Pesquisa, Assistência Técnica e Extensão Rural (Incaper).