Bioactive Neolignans and Other Compounds from Magnolia grandiflora L.: Isolation and Antiplasmodial Activity

Abstract

Bioassay-guided fractionation of a methanol extract of Magnolia grandiflora against Plasmodium falciparum yielded two new (1 and 2) and six known (3 – 8) bioactive compounds. The structures of the new compounds were assigned by mass spectrometric and 1D and 2D NMR data. Known compounds were identified by comparison of 1H NMR and MS data with literature data. The two known neolignans 3 and 4 showed moderate antiplasmodial activity with IC50 values of 2.8 ± 0.1 and 3.4 ± 0.1 μM, respectively. Weak antiplasmodial activity was recorded for compounds 1, 2, 5, 6, 7 and 8, with IC50 values of 38 ± 2, 23 ± 2, 16.5 ± 0.2, 86 ± 1, 44 ± 4 and 114 ± 9 μM, respectively.

The value of universally available raw NMR data for transparency, reproducibility, and integrity in natural product research

“…Structural revision can occur at three points of scientific discovery, preferably prior to publication, either in the originating laboratory or at the manuscript review process, or less ideally post publication. One example which was only published after an initial misassignment was discovered in house is represented by the neolignan from Magnolia grandiflora L 21. This is an excellent example of the Rubik's cube philosophy discussed above.…”

“…The structure, 1 , originally proposed on the basis of HRMS, 1 H NMR and 13 C NMR was questioned on the basis of biosynthetic considerations. A further examination of 2D NMR, specifically one-bond and long-range correlations from HMBC and HSQC experiments, respectively led to a revision to structure 2 ,21 but this revision would not have been possible from the 1D data alone. In most cases of Structure Revision that see the light of day, the initial incorrect structure is not corrected in-house but published as such, and correction comes when another group isolates and/or studies the same compound.…”

Antiplasmodial natural products: an update

“…Honokiol, which is structurally similar to 347 but is not methoxylated, was six times less active (IC 50 = 16.5 µM). However, magnolol, which is isomeric to honokiol, was only slightly less active (IC 50 = 3.4 µM) than 347 , while an additional methoxy group on magnolol (3-methoxymagnolol) resulted in a 30 fold decrease in activity [217]. More SAR studies are needed to fully understand the effect of substituents on the antiplasmodial activity of simple neolignans.…”

GC/MS‐Based Fingerprinting Reveals Two Chemotypes in the Leaf Essential Oils fromMagnolia grandifloraTrees within The Urban Forestry of a Colombian Andean Plateau

“…[5] Previous studies on M. grandiflora have led to the isolation and identification of various kinds of compounds, including alkaloids, [6] sesquiterpenoids, [7 -9] sesquiterpene lactones, [10,11] flavonoids, [12] lignans [13] and neolignans. [14][15][16] Additionally, several studies have focused on the composition of volatile fractions and essential oils of different plant parts. Identified main volatile compounds in flowers include 2-phenylethanol, (2E,6Z)-farnesol, β-pinene, geraniol, germacrene D, (E)-β-ocimene, β-elemene, bicyclogermacrene, bornyl acetate, β-caryophyllene, and γacoradiene.…”

“…M. grandiflora has well‐known uses in American indigenous medicine as bitter tonics, antimalarials, and diaphoretics, [4] as well as in traditional Chinese medicine, in which the use of leaves for the treatment of hypertension has been reported [5] . Previous studies on M. grandiflora have led to the isolation and identification of various kinds of compounds, including alkaloids, [6] sesquiterpenoids, [7–9] sesquiterpene lactones, [10,11] flavonoids, [12] lignans [13] and neolignans [14–16] . Additionally, several studies have focused on the composition of volatile fractions and essential oils of different plant parts.…”