Biological screening of herbal extracts and essential oil from Plectranthus species: α-amylase and 5-lipoxygenase inhibition and antioxidant and anti-Candida potentials

Abstract The phenolic compound content, the antioxidant and α-amylase inhibition potentials of different extracts of the Plectranthus amboinicus, P. barbatus and P. ornatus were evaluated. We also evaluated the influence of plant growth and harvest time on the chemical composition of the essential oil (EO) of P. amboinicus, its antioxidant and anti-Candida activities and the α-amylase and lipoxygenase inhibitions. The turbo-extract of P. barbatus showed the greatest phenolic compound content and antioxidant activity. No α-amylase inhibition activity was observed in the analyzed extracts, but the turbo-extraction and refluxing extracts possessed high antioxidant activities. Protected cultivation and morning harvest conditions gave the best antioxidant activities, which was associated to the highest carvacrol content. P. amboinicus EO antioxidant activity could contribute to the reduction of oxidative stress in diabetes. Causal Candida strains of diabetic foot ulcers showed sensitivity to P. amboinicus EO. C. albicans and C. dubliniensis were the most sensitive of the selected Candida strains. Turbo-extracts or refluxing of the three species extracts and the EO of P. amboinicus should be considered as a potential candidate for the management the complications of type 2 diabetes.

Proteção do dano oxidativo hepático induzido por ferro pelo extrato aquoso da planta Plectranthus barbatus / Protection against hepatic oxidative damage induced by iron by the aqueous extract of Plectranthus barbatus

Plectranthus barbatus Andrews (Lamiaceae) é uma planta muita utilizada na medicina popular para o tratamento de doenças gastrointestinais e hepáticas. O objetivo do presente trabalho foi estudar o efeito protetor do extrato aquoso de P. barbatus (EAPB) sobre os danos hepáticos causados pela sobrecarga de ferro provocada pelo ferro-dextran em ratos. O tratamento com ferro-dextran induziu uma redução significativa na concentração de glutationa reduzida nos animais tratados em relação ao grupo controle e o tratamento prévio dos animais com o EAPB protegeu o fígado do efeito provocado pelo ferro neste parâmetro. Com relação à lipoperoxidação, houve aumento significativo na concentração de malondialdeído (MDA) nos animais tratados em relação ao controle, entretanto, quando os animais receberam o tratamento prévio com o EAPB, houve redução significativa na concentração do MDA. A análise histopatológica mostrou que o grupo tratado com ferro-dextran apresentou grânulos de ferro no citoplasma das células de Kupffer com alargamento das mesmas e algumas com os núcleos hipertróficos. O tratamento prévio com EAPB resultou no desaparecimento dos sinais de danos às células de Kupffer sem nenhum núcleo hipertrófico, mas com a presença de grânulos de ferro totalmente fagocitados, o que demonstra uma aparência morfológica normal. Portanto, o EAPB pode ser útil na prevenção de danos hepáticos induzidos por sobrecarga de ferro.

The Plectranthus barbatus Andrews (Lamiaceae) is a plant largely used in folk medicine to treat gastrointestinal and liver diseases. The objective of this work was to study the protective effect of the aqueous extract of P. barbatus (EAPB) against damage caused by iron overload induced by iron dextran in rat liver. Treatment with iron-dextran induced a significant reduction in the glutathione levels in treated animals compared to control group, and the pretreatment of animals with EAPB protected the liver from the effects caused by iron in this parameter. With respect to lipid peroxidation, a significant increase in the malondialdehyde (MDA) levels in treated animals compared to control was observed; however, when the animals were pretreated with EAPB, there was a significant reduction in the MDA levels. Histopathological analysis showed that the group treated with iron-dextran showed iron granules in the cytoplasm of the Kupffer cells and some of them presented enlarged nuclei. The group previously treated with EAPB showed the disappearance of the signs of damage to the Kupffer cells with no nucleus hypertrophy but with the presence of iron granules completely phagocytosed by these cells, which showed a normal morphological appearance. Therefore, the EAPB may be useful in the prevention of liver damage induced by iron overload.