Important nodes can be identified based on their position within the network. The assumption is that changes in the key positions of a network will have more impact on the network than changes on marginal or relatively isolated positions.
MetaboAnalyst provides two well-established node centrality measures to estimate node importance - degree centrality and betweenness centrality.
In a graph network, the degree of a node is the number of connections it has to other nodes. Nodes with higher node degree act as hubs in a network. The betweenness centrality measures the number of shortest paths going through the node. It takes into consideration the global network structure.
For example, nodes that occur between two dense clusters will have a high betweenness centrality even if their degree centrality values are not high. Note, you can sort the node table based on either degree or betweenness values by double clicking the corresponding column header.