Experimental and Computational Crystal Structure Landscape Study of Nigerloxin: a Fungal Metabolite from Aspergillus niger.

The crystal structure landscape for the bioactive fungal metabolite, nigerloxin, had
been explored in the present study using a combined experimental and computational approach.
Two new solvate forms of nigerloxin, had been identified from the crystallization screening
experiments. Additionally, a crystal structure prediction (CSP) of nigerloxin anhydrate and
monohydrate forms had been performed in the study. A comparison of the radical scavenging
properties of nigerloxin and related β-hydroxy-γ-pyrone analogues have been performed with the
help of bond dissociation enthalpy (BDE) and HOMO-LUMO energy gap computations which
indicate lowest BDE and HOMO-LUMO gaps for nigerloxin. Various growth units present in the
experimental and predicted crystal structures were identified using the supramolecular synthon
approach and were utilized in the identification of most probable crystal growth pathways
available for nigerloxin. A total of twelve distinct crystal growth pathways were identified for
the nigerloxin anhydrate from the CSP based crystal structural landscape study. The 1-D
nigerloxin water tape synthon (1HA) was identified as the most frequently observed growth unit
in the predicted structures and was also found present in the two experimental solvate forms. The
higher order supramolecular constructs derived from the synthon, 1HA were identified as the
most probable crystal growth pathways for the putative monohydrate forms of nigerloxin.