Chemical Constituents and Biological Activities of Plants from the GenusNeolitsea

Chemical Constituent of β-Glucuronidase Inhibitors from the Root of Neolitsea acuminatissima

Neolitsea acuminatissima (Lauraceae) is an endemic plant in Taiwan. One new carboline alkaloid, demethoxydaibucarboline A (1), two new eudesmanolide-type sesquiterpenes, methyl-neolitacumone A (2), neolitacumone E (3), and twelve known compounds (4-15) were isolated from the root of Neolitsea acuminatissima. Their structures were elucidated by spectroscopic analysis. Glucuronidation represents a major metabolism process of detoxification for carcinogens in the liver. However, intestinal bacterial β-Glucuronidase (βG) has been considered pivotal to colorectal carcinogenesis. To develop specific bacterial-βG inhibitors with no effect on human βG, methanolic extract of roots of N. acuminatissima was selected to evaluate their anti-βG activity. Among the isolates, demethoxydaibucarboline A (1) and quercetin (8) showed a strong bacterial βG inhibitory effect with an inhibition ratio of about 80%. Methylneolitacumone A (2) and epicatechin (10) exhibited a moderate or weak inhibitory effect and the enzyme activity was less than 45% and 74%, respectively. These four compounds specifically inhibit bacterial βG but not human βG. Thus, they are expected to be used for the purpose of reducing chemotherapy-induced diarrhea (CID). The results suggest that the constituents of N. acuminatissima have the potential to be used as CID relief candidates. However, further investigation is required to determine their mechanisms of action.

Immunomodulatory Effects of Taiwanese Neolitsea Species on Th1 and Th2 Functionality

Neolitsea species, medicinal plants belonging to Lauraceae, contain rich alkaloids, steroids, sesquiterpenoids, and triterpenoids which possess antimicrobial, antioxidant, and anti-inflammatory bioactivities. However, species differences in the immunomodulatory effects and evidence pertaining to the effects of Neolitsea species on adaptive immunity are scarce. This study aimed to evaluate the immunomodulatory properties of ten Taiwanese Neolitsea plants on T helper (Th) cell functionality, especially Th1 and Th2. Most of the 29 crude extracts of Neolitsea were not toxic to splenocytes, except N. buisanensis roots. N. aciculata and N. villosa leaf extracts possessed differential immunomodulatory effects on Th1/Th2 balance. N. aciculata var. variabillima and N. hiiranensis leaf extracts attenuated both Th1 and Th2 cytokines while N. konishii dramatically suppressed IFN-γ production. As N. aciculata var. variabillima and N. konishii leaf extracts significantly attenuated Th1 functionality, we further evaluated their effects on CD4 cells under CD3/CD28 stimulation. N. aciculata var. variabillima significantly suppressed IFN-γ, IL-10, and IL-17, demonstrating the broad suppressive effects on T helper cells; N. konishii significantly suppressed IFN-γ and IL-10 production, while the production of IL-17 was not altered. Collectively, these data demonstrated that leaf extracts of Taiwanese Neolitsea species contain phytochemicals with potentials to be developed as selective immunomodulators.

Chemical Composition, Antibacterial and α-Glucosidase Inhibitory Activities of the Essential Oils of Neolitsea coccinea (Lauraceae)

The chemical composition, antibacterial and α-glucosidase inhibitory activities of the essential oils obtained from hydrodistillation of the fresh stem and leaf of Neolitsea coccinea B. C. Stone are reported for the first time. GC and GC-MS analysis revealed the presence of 42 volatile compounds from the stem and leaf oils, accounting for 84.9% and 90.4%, respectively of the identified components. The principle compounds in the stem oil were δ-cadinene (21.2%), 1-epi-cubenol (11.3%) and cyperotundone (10.7%), while the main compounds in the leaf oil were selin-11-en-4-α-ol (26.8%), bicyclogermacrene (12.6%), γ-eudesmol (7.1%), germacrene D (6.1%) and globulol (5.9%). The leaf oil demonstrated moderate to weak antibacterial activity towards Bacillus subtilis and Staphylococcus aureus with MIC values of 250 μg/mL and 500 μg/mL, respectively, whereas the stem oil possessed weak antibacterial activity against B. subtilis with a MIC value of 500 μg/mL. The stem and leaf oils showed significant α-glucosidase inhibitory activity with IC50 values of 32.2 ± 0.8 μg/mL and 70.9 ± 1.1 μg/mL, respectively.