CHEMICAL CHARACTERIZATION OF LIGNANS FROM Araucaria araucana A NATIVE CONIFER OF CHILE AND EVALUATION OF THEIR CYTOTOXICITY AND ANTIOXIDANT ACTIVITIES

Abstract

Araucaria araucana is a native conifer of Chile commonly called Araucaria. The knots of Araucaria are extremely hard wood and highly rot-resistant, they can be found in the forest decades after that the tree has dead and decomposed. Here we report the phytochemical characterization of different parts of the Araucaria as stemwood, branch and knots, founding a remarkable difference in the content of extractables in these parts, as well as the lignan composition, which is higher in knots than in branches or stemwood. Eudesmin was isolated and crystallized from organic extract of knots, its structure was determinate by NMR; moreover, secoisolariciresinol, lariciresinol and matairesinol were identified by GCMS and HPLC in contrast to standards, and quantified in stemwood, branch and knots. The results showed that secoisolariciresinol is the main lignan with 45.77 mg g-1 , followed by eudesmin with 22.68 mg g-1 , lariciresinol 4.57 mg g-1 and matairesinol with 1.19 mg g-1. The antioxidant activity in terms of DPPH assay showed that knotwood extract displays the higher activity, meanwhile that eudesmin did not displays activity in DPPH assay. The cytotoxic activity against SHSY5Y neuroblastoma and P3X myeloma cell lines, revelated a moderate activity of extracts, while eudesmin did not showed activity.

Neuroprotective Properties of Eudesmin on a Cellular Model of Amyloid-β Peptide Toxicity

“…It has been reported that other lignan similar to Eu, Sesamin, has showed neuroprotective effects involving anti-inflammatory paths [50,51]. We isolated Eu from Araucaria araucana, a native conifer from Chile that indigenous people have used as food and traditional medicine [41]. Eu did not show toxicity in the concentration range investigated (1-1000 nM), using a cellular viability assay (Supplementary Figure 1).…”

“…Soxhlet extraction was made with 2-5 g of sample placed in a cellulose thimble with acetone (250 mL) and refluxed for 12 h. The organic layer was filtered through a GV Durapore filter (0.22 m pore size, 13 mm diameter, Millipore, Bedford, MA, USA) and evaporated under reduced pressure, and dried in vacuum to give the extract. Subsequently, isolation of Eu (yield 1% w/w) was obtained after dissolve the extract in hot ethanol (70 • C) and kept in cold in 4 • C for 8 h. Eu was frozen at -20 • C until use with a 96-98% purity as previously described [41].…”

“…Additionally, these privileged natural scaffolds have been studied as potential phytohormones for, among others, the treatment or prevention of cancer and neuroprotective properties [38]. Different type of lignans have been isolated from almost all vascular plants, but their specific role is not entirely understood [41]. It has been suggested that they are part of the plants' defense system against pathogens [2,3].…”

“…Moreover, Eu has been reported mainly from the genus Artemisia, exhibiting nitric oxide (NO) inhibitory effects and cytotoxic activities [39,40]. In the present study, we use Eu isolated from the wood of Araucaria araucana, a Chilean native species to evaluate its neuroprotective abilities using an in vitro model of AD with A␤ soluble oligomers treatments [41]. We investigated the cells viability response, presynaptic preservation, and established a direct relationship with calcium transient recordings and presynaptic markers.…”

NMR Characterization of Lignans

“…A recent contribution in the characterization of lignans from the A. araucana plant, growing in Chile over 2000 m, is due to Bravo-Arrepol [ 21 ]. The knots (picoyo) of this tree are made of extremely hard wood, and with respect to A. angustifolia knots enriched in lignans; the latter has not been well characterized.…”