Cytotoxic activity fo four xanthones fromEmericella variecolor, an endophytic fungus isolated fromCroton oblongifolius

Abstract

Four xanthones were isolated from mycelia of Emericella variecolor, an endophytic fungus isolated from the leaves of Croton oblongifolius. Their structures were elucidated by spectroscopic analysis to be shamixanthone, 14-methoxytajixanthone-25-acetate, tajixanthone methanoate, and tajixanthone hydrate. All compounds were tested for cytotoxic activity against various human tumor cell lines including gastric carcinoma, colon carcinoma, breast carcinoma, human hepatocarcinoma, and lung carcinoma. The antitumor activities of these xanthones were compared with that of doxorubicin hydrochloride, a chemotherapeutic substance. All of them showed moderate activities and were selective against gastric carcinoma, colon carcinoma, and breast carcinoma. Only tajixanthone hydrate exhibited moderate activity against all cancer cell lines. Furthermore, under the test conditions it was found that 14-methoxytajixanthone-25-acetate and tajixanthone hydrate are almost as active as doxorubicin hydrochloride against gastric carcinoma (KATO3) and breast carcinoma (BT474).

New Prenylxanthones from the Deep-Sea Derived Fungus Emericella sp. SCSIO 05240

“…The NMR spectra revealed the same prenylxanthone skeleton of 3 as those of 1 , 2 and 8 . The 1 H and 13 C NMR spectra of 3 (Table 1 and Table 2) were much similar to those of tajixanthone methonate ( 10 ) [11] except for the additional methoxy signal δ H 3.48 (3H, s, OCH 3 ) corresponding to C-15. One more methoxy signal δ H 3.29 (3H, s, OCH 3 ) was found to be connected to C-16, as same as that of 10 .…”

“…The NMR spectra revealed the same prenylxanthone skeleton of 4 as those of 1 – 3 . The 1 H and 13 C NMR spectra of 4 (Table 1 and Table 2) were much close to those of tajixanthone hydrate ( 6 ) [11], except for the additional acetate group (δ C 170.3, 20.7; δ H 1.84, 3H, s) connected to C-15 (δ C 78.6; δ H 5.17, 1H, dd, J = 10.5, 3.0 Hz). The multiplicity and coupling constant values for H-14a, H-14b, and H-15 of 4 were very similar to those of 3 and 6 , suggesting the same relative stereochemistry for these compounds.…”

“…Six known prenylxanthones were identified as shamixanthone ( 5 ) [11], tajixanthone hydrate ( 6 ) [11], ruguloxanthone A ( 7 ) [12], ruguloxanthone B ( 8 ) [12], tajixanthone ( 9 ) [13], and tajixanthone methonate ( 10 ) [11], by comparison with their 1 H and 13 C NMR with those reported (Figure 3). In order to confirm the absolute configuration of prenylxanthones skeleton, the X-ray crystallographic analysis of ruguloxanthone B ( 8 ) was carried out (Figure 4).…”

“…The configuration at C-15 is same as taxjixanthone hydrate ( 6 ), on the basis of comparison of optical rotation data [−78.1 ( c 0.0031, CHCl 3 )] of 1 and [−76.0 ( c 0.23, CHCl 3 )] of 6 [11]. Thus, the compound was determined as 16-chlorotajixanthone hydrate, as shown in Figure 5, and named as emerixanthone A ( 1 ).…”

“…Prenylxanthone derivatives have also been found in other Emericella fungi, such as E. rugulosa [12] and E. variecolor ( Aspergillus variecolor ) [11,13]. The biosynthesis of tajixanthone ( 9 ) and related metabolites of A. variecolor has been studied by incorporation experiments, and it provided further circumstantial evidence that this group of metabolites was biogenetically related to tajixanthone ( 9 ) and shamixanthone ( 5 ) [15].…”