Knipholone cyclooxanthrone and an anthraquinone dimer with antiplasmodial activities from the roots of Kniphofia foliosa

Antiplasmodial Quinones from the Rhizomes of Kniphofia Foliosa

“…The molecular ion peak at m/z 474.1303 (corresponding to C 27 H 22 O 8 ) and lack of OH signals (except for the chelated hydroxyl groups), even in acid free solvent, is in agreement with cyclization involving C-10 and 6'-OH, as in kinipholone cyclooxanthrone [10]; consequently, the new compound was characterized as 10-acetonylknipholone cyclooxanthrone (1). This compound appears to have been formed through the acetonation of knipholone cyclooxanthrone, a compound which was recently isolated from the roots of this plant [10]. There are examples of compounds reported from plants containing a three carbon substituent, including acetonides, probably derived from propanoyl-CoA [11]; however, there still exists controversy as to whether acetonides are true natural products or artifacts formed during extraction and isolation [12].…”

Cytotoxic Compounds from Aloe megalacantha

“…Compound 3 was isolated as yellow amorphous powder and was assigned the molecular formula C 31 H 22 O 9 based on the HR-ESI-MS analysis (negative mode; [M − H] − m / z 537.1863) and 13 C-NMR data ( Table 1 ). The positive mode of HR-MS did not show the molecular ion peak, instead the demethoxylated pseudo molecular ion peak [M – OCH 3 ] + ( m / z = 507.1034) was observed similar to the related dimeric anthraquinones [ 9 , 12 ]. Its UV–vis spectrum showed characteristic absorptions (λ max 215, 261, 384, 432 nm) consistent with an anthrone-anthraquinone dimer [ 14 ].…”

“…The position of one methoxy group (δ H 3.93; δ C 56.1) was established at C-6′ (δ C 148.0) according to its HMBC correlation to C-6′, while the hydroxy group at δ H 5.84 showed a correlation to C-7′ (δ C 146.9). The other methoxy group (δ H 3.66; δ C 51.6) corresponds to a methyl ester deduced from its upfield shifted (δ C 51.6) signal [ 12 ] and from its HMBC correlation with the ester carbonyl (δ C 174.5). Comparison of these spectroscopic data with the literature revealed that the compound was very similar to ω-feruloyloxyacid [ 27 ] and ethyl 24-(feruloyloxy)docosanoate [ 28 ].…”

“…While the genus Aloe is the most extensively investigated species due to its rich medicinal value and chemotaxonomic aspect, no phytochemical analysis and biological activities of A. megalacantha have been reported. Thus, as part of our ongoing search for new bioactive natural products of plants from the Asphodelaceae family [ 11 , 12 , 13 ], we report the isolation of four new natural products 1 – 4 , along with ten known compounds (one coumarin and nine anthraquinones). The cytotoxicity of the compounds against the human cervix carcinoma cell line KB-3-1 is also reported.…”

Naturally occurring naphthalenes: chemistry, biosynthesis, structural elucidation, and biological activities

“…Compound 6 exhibited anti-malarial activity with an ED 50 value of 15.4 lg/ mL against P. falciparum (Abraham et al 2005). Compound 7 showed anti-plasmodial activity against chloroquine resistant (W2) and chloroquine-sensitive (D6) strains of P. falciparum (Abdissa et al 2013). Moreover, compounds 60 and 64 exhibited activity against P. falciparum with IC 50 values of 11.45 and 6.85 lM, respectively (Wongsa et al 2013).…”