Evaluation of toxicity of some saponins on brine shrimp

General Access to Modified α-Amino Acids by Bioinspired Stereoselective γ-C-H Bond Lactonization

α-Amino acids represent a valuable class of natural products employed as building blocks in biological and chemical synthesis. Because of the limited number of natural amino acids available, and of their widespread application in proteomics, diagnosis, drug delivery and catalysis, there is an increasing demand for the development of procedures for the preparation of modified analogues. Herein, we show that the use of bioinspired manganese catalysts and H₂ O₂ under mild conditions, provides access to modified α-amino acids via γ-C-H bond lactonization. The system can efficiently target 1°, 2° and 3° γ-C-H bonds of α-substituted and achiral α,α-disubstituted α-amino acids with outstanding site-selectivity, good to excellent diastereoselectivity and (where applicable) enantioselectivity. This methodology may be considered alternative to well-established organometallic procedures.

Two new nortriterpenoid saponins from Salicornia bigelovii Torr. and their cytotoxic activity

Investigation of characteristic constituents of Salicornia bigelovii Torr. led to isolation of two new 30-nortriterpenoid glycosides, Bigelovii A (1), Bigelovii B (2), together with two known 30-nortriterpenoid glycosides 3-4 and three known oleanane-type triterpenoid glycosides 5-7. The structures of new compounds were elucidated by extensive 1D and 2D NMR, and MS spectroscopic analysis, and chemical evidences. All compounds were isolated for the first time from Chenopodiaceae. Thus compounds 1-4 were evaluated for their cytotoxicity and compouds 1, 3 showed moderate activity against four cell lines, HL-60 (promyelocytic leukemia), MCF-7 (breast carcinoma), HepG2 (liver carcinoma) and A549 (lung carcinoma), with IC(50) values of 6.18, 78.08, 13.64 and >100μM for 1; 31.87, >100, ~100, >100μM for 3, respectively.

The good and the bad: alkaloid screening and brineshrimp bioassays of aqueous extracts of 31 medicinal plants of eastern Nicaragua

CONTEXT

Presence/absence tests for alkaloids of 31 medicinal vascular plant species from 31 genera and 26 families of eastern Nicaragua provided a baseline for bioactivity tests.

OBJECTIVE

To determine the bioactivity and cytoxicity of aqueous extracts of widely used medicinal species in eastern Nicaragua.

MATERIALS AND METHODS

Ethnomedicinal applications were obtained from interviews of traditional healers. We used Dragendorff's reagent to test alkaloids and brine shrimp for cytotoxicity of aqueous extracts.

RESULTS

Twenty-nine of the 31 species tested positive for alkaloids. The median lethal concentration that kills 50% of the larvae within 24 h of contact with the extract (LC(50) was less than 1000 µg/mL for 4 (13%) species (the usual cytotoxic category), 1001-5000 µg/mL for 23 (74%) species, and between 5001-7500 µg/mL for the remaining 4 (13%) species.

DISCUSSION AND CONCLUSION

Twenty-five of the ethnomedicines contain alkaloids but are not cytotoxic. In contrast to first suppositions, we suggest that this is a good and desirable, and perhaps expected, outcome. Medicinal plants that are cytotoxic may obviously control or kill bacteria or other pathogens, but may also negatively affect the patient; some high alkaloid levels have been associated with carcinogens. Thus, perhaps the majority of effective medicinals should be expected to be noncytotoxic. We suggest that this is a new paradigm for consideration of the overall value and effectiveness of medicinals. Of course, medicinals also can be effective in numerous ways (e.g., organ stimulation or other physiological functions) other than simply as antimicrobials or antipathogens.

Cytotoxic constituents from the bark of Salix hulteni

Eight compounds were isolated from the bark of Salix hulteni. Based on spectral data, the isolated compounds were identified as 4-hydroxyacetophenone (1), naringenin (2), aromadendrin (3), catechin (4), picein (5), sachaliside 1 (6), 1-p-coumaroyl-beta-D-glucoside (7), and dihydromyricetin (8). Their cytotoxic activities against brine shrimp and a human lung cancer cell line (H1299) were evaluated.