Bioactivity-guided isolation and structural characterization of the antifungal compound, plumbagin, from Nepenthes gracilis

Figures & data

Figure 1. Nepenthes gracilis Korth.

Table 1. MIC and MFC values of extracts from different solvents and isolated plumbagin from the leaves of N. gracilis against six types of fungi.

	MIC (μg/mL)								MFC (μg/mL)
Fungi	Hex	CH	EA	ET	MT	AQ	B1	Ref	Hex	CH	EA	ET	MT	AQ	B1
C. albicans	20	313–625	625	313	313	2500	2	2	20	625	NA	NA	NA	NA	2
C. parapsilosis	20	1250	625	313–625	2500	NA	8	4	160	2500	NA	NA	NA	–	16
I. orientalis	20	313	313	160	80–160	40–80	2	4	20	313	NA	NA	NA	NA	2
C. neoformans	20	313–625	313	160	40–80	40	4	0.125	160	1250	2500	2500	NA	NA	8
A. brasiliensis	40–80	1250	NA	NA	NA	NA	31	2	160	NA	–	–	–	–	63
T. mentagrophytes	20	313	1250–2500	NA	NA	NA	2	8	20	313	2500	–	–	–	4

The results are shown as the mean or range values of triplicates. Hex, hexane extract; CH, chloroform extract; EA, ethyl acetate extract; ET, ethanol extract; MT, methanol extract; AQ, water extract; B1, plumbagin; Ref, reference drug, amphotericin B; NA, no activity; “–”, not tested since no MIC value was obtained.

Table 2. MIC and MFC values of different fractions and compounds isolated from F₁ of the hexane extract of N. gracilis.

	MIC (μg/mL)		MFC (μg/mL)
Fraction/compound	T. mentagrophytes	C. neoformans	T. mentagrophytes	C. neoformans
Hexane fraction (F1)	8	16	8	16
B1	2	4	4	8
B2	62.5	125	125	NA
Ethyl acetate fraction (F2)	16	31	16	31
Water fraction (F3)	NA	NA	–	–
Ref	8	0.125

The results are shown as the mean values of triplicates. The meaning of the abbreviations are as follows: B1, 1st compound isolated from F₁; B2, 2nd compound isolated from F₁; Ref, reference drug, amphotericin B; NA, no activity; “-”, not tested since no MIC value was obtained.

Figure 2. Cytotoxic effects of isolated plumbagin from N. gracilis on rhesus monkey kidney epithelial cells (LLC-MK2). LLC-MK2 cells were treated with various concentrations (0.05–6.25 μg/mL) of plumbagin for 72 h. The results represent mean ± standard deviation of three replicates. *Statistically significant (p < 0.05) with one-way ANOVA.